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LABORATORY  GUIDE 


PHYSIOLOGY 


WiNFIELD  S.  HALL,  Ph.  D.,  M.  D., 

PROFESSOR  OF  PHYSIOLOGY,   NORTHWESTERN  UNIVERSITY  MEDICAL  SCHOOL 

CHICAGO. 


with    appendices     on     organiz.v 
tion    and    Equipment. 


TWO     COLORED     PLATES 

AND 

SIXTY  ILLUSTRATIONS. 


Chicago  Medical  Book  Co. 

35-37  Randolph  Street, 

1897 


Copyright,  1897, 
By  Winfield  S.   Hall. 


Hl4 


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PREFACE. 


American  laboratories  of  physiology  have  usually  been 
established  in  medical  schools  after  these  institutions  have 
already  associated  histology  with  pathology,  and  physio- 
logical chemistry  with  general  chemistry.  The  problems 
presented  in  those  American  laboratories  of  physiology, 
which  are  departments  of  medical  schools,  are,  therefore, 
essentially  the  physical  problems  of  physiology.  And 
such  are  the  problems  which  occupy  the  major  part  of  this 
manual.  The  student  who  has  but  four  years  to  devote  to 
the  study  of  medicine  cannot  consistently  be  assigned 
more  than  100  hours  to  120  hours  of  laboratory  work  in 
physical  physiology.  How  to  most  profitably  spend  this 
brief  period  is  a  question  which  has  engaged  the  attention 
of  the  writer  for  a  number  of  years. 

In  the  choice  of  the  work  to  be  assigned  to  the  student 
it  has  been  taken  for  granted  that  he  has  entered  upon 
his  study  of  medicine  with  a  working  knowledge  of  physics 
and  of  Algebra,  and  that  laboratory  work  in  physiology  is 
not  begun  until  the  student  has  made  considerable  prog- 
ress in  gross  and  minute  anatomy.  Courses  in  anatomy 
and  physiology  should  be  so  coordinated  as  to  enable  the 
student  to  gain  a  thorough  knowledge  of  the  morphology 
of  an  organ  before  he  experiments  upon  its  function. 

The  method  of  presentation  is  purely  inductive.  The 
student  is  given  the  technique  and,  through  a  series  of 
questions,  he  is  guided  in  his  observations.  Me  is  not, 
however,  told  what  he  is  expected  to  observe,  nor  is  he  told 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 

what  his  conclusions  are  expected  to  be.  On  these  points 
he  is  left  on  his  own  resources.  Repeated  trial  of  this 
method  with  different  classes  proves  it  to  be  most  satisfac- 
tory both  to  the  instructor  and  to  the  student.  It  gives  to 
both  free  play  for  originality  and  individuality. 

The  manual  as  here  presented  is  far  from  complete. 
Should  a  second  edition  be  justified,  it  will  contain  in  addi- 
tion to  the  present  matter,  chapters  on  Metabolism  and 
Animal  Heat ;  Excretion;  The  Voice  and  Hearing;  The  Cen- 
tral Nervous  System;  and,  An  Introduction  to  Physiological 
Psychology. 

The  Author  acknowledges  his  indebtedness  to  the 
Chicago  Laboratory  Supply  Co.  and  to  Richards  &  Co.  for 
the  cuts  used  in  Appendix  C.  He  takes  this  opportunity 
to  express  his  thanks  to  Dr.  W.  K.  Jaques  for  preparing 
the  chapter  on  Physiological  Hematology,  and  to  Mrs. 
Jaques  for  illustrating  the  same;  to  Dr.  H.  M.  Richter  for 
the  chapter  on  Pharmacology;  to  Dr.  A.  M.  Hall  for  the 
lessons  on  Normal  Ophthalmoscopy  and  Skiascopy;  and  to 
Miss  N.  S.  Hall  for  the  illustrations  of  the  first  six  chapters. 

The  Author. 
Chicago,  Sept.  30,  189V. 


Table  of  Contents. 


INTRODUCTION. 


PART  I.     GENERAL  PHYSIOLOGY. 


A.  The  physiology  of  ciliary  motion. 

I.   a.  Normal  Ciliary  Motion 1G 

b.   Ciliary    Motion    Modified    by   the  Influ- 
ence of  Narcotics  and  Stimulants. 
II.   To  Determine  the  Amount  of  Work  done 

by  Cilia , 23 

B.  The   general   physiology  of  muscle  and   nerve  tissue. 

III.    a.   Elements  and  Conductors. 

b.  Keys. 

c.  Commutator. 

d.  Work  done  by  the  Cell  or  Element. 

e.  Electrical  Units  of   Measurement 26 

IV.   Batteries;     Cells    in     Multiple    Arc    or    in 

Series;    Relation   of   the   Current   to   the 

Method  of  Joining  the  Cells 30 

V.  Methods  of  Varying  the  Strength  of  Cur- 
rent       40 

a.  The  Rheostat. 

b.  The  Du  Bois-Reymond  Rheocord. 

VI.  To  Vary  the  Strength  of  Current  through 
the  Use  of  {a)  the  Simple  Rheocord,  or 
of  (/> )  the  Ludwig  Compensator 43 


LABORATORY  GUIDE  JX  PHYSIOLOGY 

VII.   To  vary  the  strength  of  an  Electric. Current 

Gradually.     Fleischl's  Rheonom 48 

VIII.    To  Determine  the  Influence  of  the  Kathode 

and  Anode  Poles 51 

IX.   a.   The  Muscle-Nerve  Preparation. 

/'.  Indirect  Mechanical,  Thermal  and 
Chemical  Stimulation  of  the  Gastroc- 
nemius        56 

X.  Variations  in  the  Method  of  Applying 
Mechanical,  Thermal  and  Chemical 
Stimuli 01 

a.  Direct  and  Indirect  Stimulation. 

b.  Qualitative  Variation  of  Stimuli. 

c.  Quantitative  Variation  of  Stimuli. 

d.  Variation  of  Length  of  Time  of  Ap- 
plying the  Stimulus. 

XL    Electricity  as  a  Stimulus.      The  Galvanic 

Current 75 

XII.    Stimulation   with    the    Constant    Current. 

The  Simple  Rheocord 68 

XIII.   The  Effect  of  Induced  Current.      Tetanus.      70 
XIV.    To  Determine  the  Amount  of  Work  Done 

by  a   Muscle 73 

a.  The  Work  Done  by  a  Single  Contrac- 
tion. 

b.  The  Total  Amount  of  Work  Done  by  a 
Muscle. 

c.  Reaction  Changes  in  Fatigued  Muscle. 
XV.   To   Determine    the  Effect    of    a  Constant 

Current  upon  the  Irritability  of  a  Nerve. 

Electrotonus 75 

XVI.    Pfliiger's  Law  of  Contraction 80 


Contents. 
PART  II.     SPECIAL  PHYSIOLOGY 


C.  The  Circulation. 

XVII.    The  Circulation  and  its  Ultimate  Cause.  . . 

a.  The  Capillary  Circulation. 

b.  To   Observe  the  Action   of   the  Frog's 
Heart. 

XVIII.  The  Graphic   Record  of  the  Frog's  Heart 

Beat 89 

XIX.  The  Apex  Beat.     The  Heart  Sounds.     The 

Cardiograph 91 

XX.  The  Flow  of  Liquids  through  Tubes.   Lat- 
eral Pressure 93 

XXI.  The  Flow  of  Liquids  through  Tubes  under 
the  Influence  of  Intermittent  Pressure. 
The  Impulse  Wave;  Graphic  Tests  ... .  98 
XXII.  The  Laws  of  Blood  Pressure  Determined 
from  an  Artificial  Circulatory  S)Stem. 
Pulse  Tracing  from  the  Artificial  System.    102 

XXIII.  The  Human  Pulse.      The  Sphygmograph. 

The  Sphygmogram 106 

XXIV.  To  Determine  the  General  Influence  of  the 

Vagus  Nerve  upon  the  Circulation 109 

D.  Respiration. 
XXV.  a.  External  Respiratory    movements 113 

b.  Intrathoracic  Pressure. 

c.  Intra-abdominal  Pressure. 

XXVI.   Respiratory  movements  in  Man 117 

a.  The  Stethograph. 

b.  The  Thoracometer. 

c.  The  Belt-Spirograph. 

d.  The  Stethogoniometer. 


LABORATORY   GUIDE  IN  PHYSIOLOGY. 

XXVII.    Respiration  in   Man 124 

a.  Lung   Capacity. 

b.  Strength  of  Inspiration  and  Expiration. 
i.    Chest  Measurements. 

ii.    Preservation  of   Data. 
XXVIII.   The  Evaluation  of  Anthropometric  Data. . .    127 
XXIX.    The   Action  of   the   Diaphragm 132 

a.  Stimulation  of  the  Phrenic  Nerve. 

b.  The  Phrenograph  and  the  Phrenogram. 
XXX    Respiratory    Pressure 136 

a.  The  Pneumatogram. 

b.  Stimulation  of   Pulmonary  Vagus. 

c.  The  Elasticity  of  the  Lungs. 

d.  The  Cardio  pneumatogram. 

XXXI.   Quantitative    Determination    of     the   COs 
and  H.,0  Eliminated  from  an  Animal  in 

a  Given  Time 140 

XXXII.   Respiration  under  Abnormal  Conditions.  .    144 

a.  Respiration   in  a  small  closed  space. 

b.  Respiration    in  a    larger  closed    Space. 

c.  Respiration  in  an  Atmosphere  of  C02. 

d.  Post-mortem  Examinations. 

XXX  III.   Respiration  in  Abnormal   Media 14  V 

a.  Respiration  in  an  Atmosphere  of   Nitro- 
gen. 

b.  Respiration  in  an  Atmosphere  of  Hydro- 
gen. 

c.  Respiration   in   an   Atmosphere    of  one- 
third  Illuminating  Gas. 

d.  Post-mortem  Examinations. 
E.   Digestion  and  Absorption. 

XXXIV.   The   Carbohydrates 153 

XXXV.   Salivary  Digestion 157 


CONTENTS.  5 

XXXVI.    The  Proteids 1G1 

XXXVII.  a.    The  diffusibility  of  Proteids 166 

b.    Milk. 

XXXVIII.  Gastric  Digestion 17  1 

XXXIX.    Gastric  Digestion,  Continued 177 

XL.  Gastric  Digestion,   Continued 180 

XLI.    The  Properties  of  Fats 182 

XLII.    Intestinal  Digestion 186 

XLIII.    Absorption 189 

F.  Vision. 

XLIV.    Dissection  of  the  Appendages  of  the  Eye.  .    191 

XLV.    Dissection  of  the  Eyeball 195 

XLVI.    Physiological  Optics 198 

a.  Determination  of  the  Indices  of  Refrac- 
tion of  Water  and  of  Glass. 

b.  Determination  of  the  Focal  Distance  of 
Lenses. 

c.  Verification  of  the  formula:   v+f^f- 

d.  Problems. 

XLVI  I.   Physiological  Optics,  Applied 210 

a.  The  Application  of  the  Laws  of  Refrac- 
tion to  the  Normal  Eye.  "  The  Re- 
duced Eye." 

b.  To  Locate,  Experimentally,  in  the  Mam- 
malian Eye  the  Cardinal  Points  of  the 
Simple  Dioptric  System. 

XLVIII.  a.    Accommodation 216 

b.    Convergence. 
XLIX.  Miscellaneous  Experiments 222 

a.  Scheiner's  Experiment. 

b.  Purkinje  Sansom's  Images. 

c.  The  Blind  Spot. 


LABOR  A  TONY  GUIDE  Itf  PHYSIOLOGY. 

d.  The  Macula  Lutea — Maxwell's  Experi- 
ment. 

e.  Shadows   of    the    Fovea    Centralis    and 
Retinal  Blood  Vessels. 

L.    Perimetry:   The  LigJit- perimeter,  the  Form- 
perimeter  and  the  Color-perimeter 226 

LI.    Determination  of  Normal  Vision 232 

a.  The  Acuteness  of  Direct  Vision. 

b.  The  Range  of  Accommodation. 

c.  The  Amplitude  of  Convergence. 

LIT.  Normal  Ophthalmoscopy — Direct  Method.  247 

a.  The  Emmetropic  Eye. 

b.  The  Hypermetropic  Eye. 

c.  The  Myopic  Eye. 

LI  1 1.  Normal  Ophthalmoscopy  —  Indirect 
Method.  The  Emmetropic,  the  Hyper- 
metropic and  the  Myopic  Eye 250 

LIV.   Skiascopy 252 

The    Emmetropic,    the    Myopic    and     the 
Hyperopic  Eye. 
G.   Physiological   Hematology. 

LV.    Examination  of  Fresh  Blood 259 

LVI.   Counting  Red  Blood  Corpuscles — Thoma- 
Zeiss  Counter 202 

LVI  I.  Counting   White    Corpuscles.      Decoloriz- 
ing the  Red  Cells 265 

LVIII.  Counting     Red     and    White    Corpuscles. 

Staining  the  White  Cells 268 

LIX.   To  Determine  the  Relative  Volume  of  Red 

Corpuscles  and  Plasma.    The  Hematocrit.  270 
LX.   Estimation   of   Haemoglobin,   v.    Fleischl's 

Haemometer 273 

LXI.    The  Microscopic  Technique  of  Hematol- 
ogy     276 


CONTENTS.  7 

a.  Spreading  Blood. 

b.  Fixing  and  Staining. 

LXII.   Differential  Counting   of  White  Cells  and 

of  Red  Cells 280 

LXII  I.    Study  of  Bone  Marrow 281 

H.  An  Introduction  to  Pharmacology. 

LXI V.  Curare 285 

LXV.  Atropin 290 

LXVI.  Pilocarpin 293 

LXVII.  Strychnin 295 

LXVIII.  Veratrin 298 

LXIX.  Digitalis 300 

LXX.  Aconite     303 

Appendix  A. 

Description  of    General    Laboratory   Appliances    and 

New  Apparatus 307 

Appendix  B. 

On  the  Organization   and   Equipment   of  the    Depart- 
ment of  Physiology 321 

Appendix  C. 

Figures  and  Brief  Descriptions  of  Instruments 333 


INTRODUCTION. 


THE  METHOD  OF    PRESENTING  THE  SUBJECT. 

REGARDING    ILLUSTRATIONS. 

The  profuse  illustration  of  a  text-book  is  in  perfect  ac- 
cord with  the  principles  of  pedagogy;  that  the  profuse 
illustration  of  a  laboratory  manual  is  the  reverse  is  evident 
from  the  following  considerations  : 

The  laboratory  student  receives  from  the  demonstrator 
the  material  with  which  he  is  to  work.  If  he  receives 
a  piece  of  apparatus  which  is  new  to  him,  a  few  questions 
or  hints  in  his  laboratory  manual  will  lead  him  to  discover, 
from  an  examination  of  the  apparatus  itself,  the  physical 
and  mechanical  principles  involved  and  utilized  in  it. 
Most  students  will  spontaneously  make  drawings  showing 
the  essential  parts  of  the  instruments;  all  students  will 
willingly  do  so  if  required.  This  is  a  most  valuable  exer- 
cise for  the  pupil,  which  is  likely  to  be  omitted  if  the 
manual  contains  cuts  of  the  apparatus. 

Nearly  ever}'  exercise  requires  the  preparation  of  some 
simple  appliance — e.  g.,  a  frog  board  or  a  recording  lever 
— whose  construction  will  be  much  facilitated  if  the  stu- 
dent is  guided  by  a  figure  in  his  manual,  but  a  model 
which  the  demonstrator  has  made  will  be  a  better  guide. 

I  have  often  seen  students  read  their  text  descriptive 
of  some  organ — e.  g.,  a  frog-heart — and  verify  its  state- 
ments from  the  accompanying  figures,  leaving  almost  un- 
noticed the  object  itself,  which  lay  before  them.  A  few 
brief  questions  or  hints  would   have  led   them  to   discover 


10  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

from  the  object  all  of  its  essential  features.  Diagrammatic 
anatomical  figures  are  sometimes  useful  in  a  laboratory 
manual,  but  true  anatomical  figures  are  worse  than  use- 
less— they  bar  the  student's  independent  progress.  If  his 
laboratory  manual  contains  illustrations  of  all  apparatus 
and  tissues,  and  of  such  experiments  as  admit  of  graphic 
records,  the  student  makes  similar  drawings  in  his  notes, 
either  unwillingly  or  dependently — frequently  both.  The 
laboratory  work  is  thus  robbed  of  much  of  the  benefit  it  is 
intended  to  give  the  student.  Independence  and  origi- 
nality are  completely  defeated  or  aborted,  except  in  the 
case  of  the  rare  student. 

If  the  laboratory  manual  contains  graphic  records  of 
experiments,  much  of  the  time  of  the  demonstrator  will  be 
consumed  in  explaining  to  the  students  individually  why 
the  same  physiological  functions  observed  with  slightly 
different  apparatus  and  under  slightly  different  circum- 
stances, may  yield  tracings  which  differ  in  minor  detail 
from  those  in  the  book.  The  energies  of  both  demonstra- 
tor and  students  will  thus  be  partially  divsrted  from  their 
legitimate  channel. 

If  there  are  no  tracings  in  the  text,  students  will  natur- 
ally, by  comparison  of  their  tracings,  discover  the  essential 
and  the  nonessential  features  and  will  seek  the  cause  of 
the  essential  features  of  their  tracings.  After  the  student 
has  made  these  independent  discoveries  he  is  in  a  position 
to  gain  the  maximum  profit  from  the  comparison  of  his 
own  tracings  with  those  which  others  have  taken,  and 
from  anj'  explanations  which  the  demonstrator  may  choose 
to  add. 

It  is  evident  then,  that,  from  a  pedagogical  stand- 
point, the  laboratory  guide  should  be  sparsely  illustrated. 
On  the  other  hand,  the  student's  notes  should  be  profusely 
illustrated. 


INTRODUCTION.  11 

REGARDING    EXPLANATIONS. 

What  has  been  said  regarding  the  illustrations  of 
apparatus  and  of  results  applies,  in  principle,  to  the  ex- 
planation of  physiological  observations.  As  wheat  is  more 
valuable  than  chaff,  so  is  the  independent  discovery  of  a 
principle  by  the  student  more  valuable  to  him  than  its  ex- 
planation by  a  book  or  instructor.  If  the  facts  to  be 
observed  and  the  principle  involved  be  detailed  and  ex- 
plained in  advance,  the  student's  power  of  independent 
observation  and  investigation  remains  undeveloped. 

THE    FUNCTION    OF    THE    DEMONSTRATOR. 

It  may  be  well  to  introduce  this  topic  by  a  statement 
of  what  the  function  of  the  demonstrator  is  not.  It  cer- 
tainly is  not  to  rob  the  student  of  the  pleasure,  exhilaration 
and  benefit  of  the  independent  investigation  of  a  problem 
by  introducing  each  laboratory  period  with  an  enumeration 
of  the  facts  and  principles  which  the  work  of  the  day  is 
expected  to  establish.  Such  an  introduction  is  worse  than 
useless.  The  desirability  of  even  asking  the  attention  of 
the  entire  class  to  introductory  remarks  on  the  general 
bearing  of  the  problem  in  hand  is  to  be  questioned.  If 
the  problem  is  well  chosen  and  the  work  in  the  physiolog- 
ical laboratory  properly  coodinated  with  that  in  the 
recitation  room  and  lecture  room  and  that  in  other  de- 
partments, its  significance  will  at  once  be  evident  to  the 
intelligent  pupil.  If  the  introductory  talk  is  omitted  the 
prompt  student  may  begin  at  once,  upon  entering  the 
laboratory,  the  problem  of  the  day,  and  will  have  a  clear 
gain  of  ten  to  twenty  minutes.  Any  supplementary  in- 
struction or  hint  may  most  profitably  and  ecomically  be 
written  upon  the  blackboard. 

Most  of  the  experiments  given  in  this  book  cannot  con- 
veniently be  performed   by  one  individual   working  alone. 


12  LABORATORY  GUIDE  IN  PHYSIOLOGY 

After  some  experimentation  it  has  been  found  most  advan- 
tageous to  divide  the  class  into  sections  not  exceeding 
thirty  students,  and  to  subdivide  these  sections  into  divi- 
sions of  three  students  each.  Each  division  is  assigned  a 
table.  The  assistant  demonstrator  places  the  material 
needed  for  any  day's  work  either  upon  the  table  or  where 
it  is  readily  accessible. 

Nothing  should  be  done  for  the  student  which  he  can 
profitably  do  for  himself.  A  small  class  with  less  limited 
time  may  easily  construct  much  apparatus  in  the  work- 
shop. No  class  is  so  large  as  to  debar  the  members  from 
the  privilege  of  constructing  frog  boards,  tracing  levers, 
etc.,  (which  may  be  done  at  the  tables)  and  of  setting  up, 
adjusting  and  readjusting  all  apparatus. 

Nothing  should  be  told  a  student  which  he  can  readily 
find  out  for  himself.  The  function  of  the  demonstrator 
is  to  guide  the  student  by  questions  and  by  hints  to  dis- 
cover facts  and  to  formulate  principles.  Extended  expla- 
nations on  the  part  of  the  demonstrator  may  instruct  the 
student,  but  they  do  not  educate  him. 

HINTS    TO    THE    STUDENTS. 

It  is  a  general  principle  that  a  student  gets  out  of  a 
course  what  he  puts  into  it,  and  with  interest.  If  he  in- 
vests (1)  intellectual  capacity,  (2)  the  spirit  of  inquiry 
and  investigation,  (3)  the  power  of  logical  reasoning,  and 
(4)  the  power  to  formulate  conclusions;  he  will  promptly 
receive  interest  upon  the  investment.  Further,  the  greater 
the  investment  the  greater  the  rate  of  interest.  This  may 
seem  inequitable,  but  it  is  inevitable. 

The  value  of  taking  full  notes  of  laboratory  experiments 
is  unquestionable.  The  following  hints  regarding  note 
taking  may  be  advantageous: 

1.     Make  a  careful    description  of  each  new    instrument 
with  which  you  work. 


INTRODUCTION.  13 

2.  Formulate  each  problem  definitely. 

3.  Describe  the  means  used  in  the  solution  of  the  problem. 

4.  Enumerate  the  facts  observed  through  the  help  of  the 

means  employed. 

5.  Seek  for  and  note  causes  and  inter  relations  or  the  facts 

as  far  as  possible. 
(J.    Differentiate  the  essential  from  the  incidental. 

7.  Formulate  conclusions  from  the  collected  data. 

8.  Make  generalizations  as  far  as  they  are  justifiable. 

Agood  note  book  should  possess  thefollowing  qualities: 

a.  It  should  be  complete,   containing  an  account  of  every 

problem  studied. 

b.  It   should    be    full,    containing    a  sufficient    amount    to 

guide  another  in  performing  the  same  experiments 
and  in  verifying  the  facts  and  conclusions  noted. 

c.  It  should  be  logically  arranged. 

d.  It  should    be  as   neat   and    artistic  as   the  student  can 

make  it  in  the  time  which  he  can  devote  to  it. 


PART  I. 

GENERAL  PHYSIOLOGY  OF  CONTRACT 
ILE  AND  IRRITABLE  TISSUES. 


15 


A.  THE  GENERAL  PHYSIOLOGY  OF  CILIARY  MOTION. 

1.  a.  Normal  ciliary  motion,    b.  Ciliary  motion  modified 

by  the  influence  of  narcotics  and  stimulants. 

a.    Normal  ciliary  motion. 

/.  Appliances. — Microscope,  cell  slide  and  cover  glass; 
normal  saline  solution  (NaCl  0.6  %,  Appendix 
A,  1);  physiological  operating  case  (App.  A,  3); 
filter    paper;  frog  or  fresh  water  clam  cr  mussel. 

2.  Preparation. — If  a  lamellibranch  be  used  one  need  only 

snip  off,  with  the  small  scissors,  a  bit  of  the  margin  of  a 
gill  and  mount  it  in  a  drop  of  normal  saline  solution 
on  a  cover  slip,  invert  the  cover  over  the  cell  of  the 
cell  slide  and  focus  under  low  power.  If  a  frog  be 
used  it  will  be  necessary  to  pith  it  as  a  preliminary 
step. 
j     Operations. —  To  pith  a  frog. 

(1).   Grasp  it  with  the  left  hand,  holding  the  legs  ex- 
tended, one  on  either  side  of  the  little  finger  in  such 
a  way  as  to  bring  the  dorsum  of  the  frog  toward  the 
palm  of  the  hand. 
(2).  With  the  thumb  and  index  finger  fix  the    frog's 

nose  and  press  it  ventrally. 
(3).  Place  the  point  of  a  narrow  bladed  scalpel  in  the 
median-dorsal  line  over  the  space  between  the  occi- 
put and  atlas,  i.  e.,  over  the  occipito-atlantal  mem- 
brane. This  point  is  most  readily  located  by  using 
the  eyes  as  a  landmark.  The  occipito-atlantal  mem- 
brane lies  at  the  apex  of  an  equilateral  triangle  whose 
base  has  its  extremities  in  the  center  of  the  cornea. 
Having  located  the  point  for  incision,  press  the 
16 


GENERAL  PHYSIOLOGY.  17 

knife  through  the  skin,  the  intervening  connective 
tissue  and  the  occipito-atlantal  membrane,  and  cut 
the  spinal  cord  transverely.     Withdraw  the  knife. 

(4)  Insert  the  apex  of  a  slender  probe  or  of  a  blunt 
needle  into  the  incision,  turning  it  sharply  forward 
so  as  to  enter  the  cranial  cavity.  By  sweeping  the 
distal  end  of  the  probe  from  side  to  side  the  con- 
tents of  the  cranial  cavity  may  be  functionally  de- 
stroyed. When  it  is  required  simply  to  pith  a  frog 
it  is  understood  that  the  operation  is  complete  as 
described  above.  It  may,  however,  frequently  be 
necessary  to  destroy  the  spinal  cord  as  well  as  the 
brain.  To  accomplish  this  insert  the  needle  as  de- 
scribed under  (4)  ;  but  turn  the  point  of  the  probe 
so  that  it  shall  enter  the  neural  canal  of  the  verte- 
brae. Pass  it  along  this  canal  to  a  point  nearly  op- 
posite the  anterior  end  of  the  ilia.  Withdraw  the 
probe. 

A  pithed  frog  can  suffer  no  pain,  but  will  respond 
reflexly  to  certain  stimuli.  A  pithed  frog  whose 
spinal  cord  is  destroyed  cannot  with  the  skeletal 
muscles  respond  reflexly  to  any  stimuli.  Having 
pithed  the  frog  and  destroyed  its  spinal  cord,  pin  it 
to  a  frog  board  with  dorsum  down,  and  legs  ex- 
tended. 

To  remove  the  oesophagus  of  a  frog. 

(1)  Place  the  head  of  the  frog  nearer  to  the  operator. 
With  forceps  lift  the  mandible  and  with  the  stronger 
scissors  sever  the  whole  floor  of  the  mouth  trans- 
versely and  as  far  posteriorly  as  possible.  Divide 
the  skin  in  the  median  line  a<,  far  posteriorly  as  the 
pubes. 

(2)  Separate  the  two  lateral  halves  of  the  sternum  by 
dividing  the  median  sternal  cartilage  and  carry  the 


18  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

incision  through  the  xiphoid  appendix  and  abdomi- 
nal walls.  Withdraw  the  pins  which  fix  the  anterior 
extremities;  separate  the  lateral  halves  of  the  ster- 
num by  lateral  traction  upon  the  legs. 

(3)  With  the  forceps  grasp  a  fold  of  the  mucous 
membrane  which  surrounds  the  puckered  anterior 
end  of  the  oesophagus.  While  making  gentle  trac- 
tion with  the  forceps,  make,  with  the  fine  scissors, 
a  circular  incision  through  the  mucous  membrane 
surrounding  the  opening  of  the  oesophagus. 

(4)  Grasp  the  pyloric  end  of  the  stomach;  sever  the 
duodenum;  lift  the  stomach  up  vertically  above  the 
sternum;  make  moderate  traction.  The  delicate  and 
elastic  submucosa  about  the  end  of  the  oesophagus 
will  yield  to  the  traction  and  the  whole  oesophagus 
will  be  readily  separated  from  the  surrounding  tis- 
sues and  wholly  removed  from  the  frog. 

(5)  Open  stomach  and  oesophagus  by  means  of  a 
longitudinal  incision  through  their  walls;  stretch 
them  upon  a  cork  board,  fixing  with  pins,  and  wash 
off  mucus  with  normal  saline  solution  and  camel's 
hair  brush.  Remove  the  excess  of  liquid  with  the 
help  of  filter  paper. 

4.    Observations. 

(1)  Place  a  small  piece  of  cork  upon  the  anterior  end 
of  the  oesophagus.  Does  the  cork  move?  II  so,  in 
what  direction  and  at  what  rate  ? 

(2)  Will  the  cork  pass  over  the  boundary  line  between 
oesophagus  and  stomach,  and  will  it  move  over  the 
surface  of  the  stomach? 

(3)  To  determine  the  cause  for  the  movement  of  the 
cork,  cut  a  minute  portion  of  mucous  membrane 
from  the  crest  of  one  of  the  folds,  place  it  in  a  drop 
of  saline  solution  as  directed  under  2  [Preparation] 


GENERAL  PHYSIOLOGY.  19 

and  examine  with  a  microscope.  If  the  preparation 
has  been  properly  made  the  margin  of  the  tissue 
should,  at  certain  points,  show  the  cause  for  the 
phenomena  above  observed.  Study  the  character 
of  the  ciliary  movements.  Describe. 
(4)  Study  ciliary  movement  with  higher  power.  It  is 
probable  that  the  first  preparation  is  not  suited  to 
observation  with  a  high  power.  If  the  cilia  cannot 
be  readily  brought  into  focus,  prepare  a  second  one 
as  follows:  From  the  ciliated  surface — clam-gill 
or  frog  oesophagus — scrape  a  few  epithelial  cells, 
with  the  point  of  a  scalpel,  place  the  minute  bit  of 
tissue  upon  a  cover  glass;  add  a  small  drop  of  saline 
solution;  gently  tease  the  tissue  with  needles,  in- 
vert the  cover  upon  a  slide,  allowing  one  edge  to 
rest  upon  a  hair,  to  avoid  undue  pressure  upon  the 
tissue. 

Focus  under  high  power  (300-600  diam.).      If  the 
preparation    is    successful    groups    of    ciliated  cells 
may  be  seen  and    the  character  of   the  ciliary  move- 
ment studied. 
b.     Ciliary    motion    modified    by  the    influence    of    nar= 

cotics  and  stimulants. 
/.  Appliances.— In  addition  to  the  appliances  enumerated 
above  under  a,  one  needs  :  A  gas  flask  and  siphon  as 
shown  in  Fig.  1.  Also  a  cell  slide  with  conducting 
tube.  (Fig.  IB.)  A  gas  generator  will  be  necessary 
unless  there  is  a  large  generator  for  general  use  by 
the  class.  HC1  25%,  marble,  chloroform,  ether,  ab- 
solute alcohol,  sealing  wax,  thread,  small  glass  tube, 
soft  parafin. 
2.   Preparation.  —  To  prepare  a  cell  slide  with  conductor. 

(1)  From  a  hard   rubber   ring,    having  an  inside  dia- 
meter   of  about    1    cm,    and    a    thickness  of  about 


20 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


2  mm.,  cut  a  radial  segment  about  2  mm.  wide. 

(2)  Clean  the  ring  and  slide  with  absolute  alcohol. 

(3)  Fix  the  ring  to  the  slide  with  sealing  wax,  placing 
the  opening  in  the  ring  toward  one  end  of  the  slide. 

(4)  Heat  the  glass  tube  and  draw  it  to  one-half  of  its 
orginal  diameter  as  shown  in  Fig.  1.  B. 

(5)  Fix  the  glass  tube  to  the  slide,  using  sealing  wax. 
The  tube  may  be  further  supported  by  a  few  turns 
of  heavy  linen  thread  drawn  tightly,  tied  and  fixed 
in  position  with  drops  of  melted  wax. 

(6)  In  order  not  to  give  too  free  vent  from  the  cell  for 


Fig.  1.     Apparatus  for  forcing  a  stream  of  gas  or  vapor  through  a  cell. 
For  description,  see  I=b  2  and  j. 

the  gas   which  enters  by  the  tube  a  bit  of  soft  para- 
fin   may  be   warmed  in  the   hand   and  worked,  with 
the   point  of  a  scalpel,  into  the  space   around  the 
end  of  the  glass  tube  leaving  only  a  little  furrow  in 
the  parafin  above  the  tube. 
j.    Operation. — Fill   the   gas   flask   full  of    water  and    dis- 
place   it  with    C03    gas.     Fill    the  siphon  and  adjust 
apparatus  as   shown  in  the  figure.      During  any  read- 
justments of  the  apparatus   the  siphon   may  be  kept 


GENERAL  PHYSIOLOGY.  21 

filled  and  ready  for  action  by  putting  on  a  screw- 
clamp  at  s.  Through  varying  the  height  of  the 
receptacle  into  which  the  siphon  dips  or  through  ad- 
justment of  the  screw  clamp  or  of  the  spring  clamp  at 
d,  the  pressure  and  the  rate  of  flow  of  gas  are  under 
perfect  control.  Prepare  a  specimen  of  cilia  for  ob- 
servation with  a  low  power  microscope.  Bring  a  good 
specimen  into  the  field,  focus  the  microscope  and  ob- 
serve the  rate  and  character  of  ciliary  movement. 
Remove  screw  clamp  at  s. 
4.  Observations. — a.     The  effect  of  C0.2  upon   ciliary  activity. 

(1)  While  observing  closely  the  normal  action  of  the 
cilia,  press  the  spring  clamp  gently  for  a  few  mo- 
ments. If  after  a  half  minute  or  more  no  noticeable 
change  takes  place  in  the  rate  of  movement  of  the 
cilia  repeat  the  dose  of  gas. 

What  is  the  effect  of    C02  gas  upon    the   activity 
of  cilia  ? 

(2)  After  the  effect  of  the  gas  has  become  apparent, 
clamp  the  tube  at  d;  disjoin  at  glass  tube  beyond  and 
gently  draw  air  through  the  cell,  thus  ventilating  it 
and  restoring  practically  the  normal  condition.  Do 
the  cilia  resume  the  normal  movement  ? 

(3)  How  many  times  may  the  cilia  be  narcotized  to 
the  point  of  complete  cessation  of  activity  and  then 
by  ventilation  be  revived  again  ? 

b.      The  effect  of  chloroform  gas  upon  ciliary  activity. 

(4  )  Clamp  tube  at  s  ;  remove  flask  from  apparatus,  fill 
flask  with  water  to  expel  C02  ;  empty  ;  drop  into 
the  flask  a  pledget  of  cotton  saturated  with  chloro- 
form, replace  flask  as  in  Fig.  1.  Make  a  new 
preparation  of  cilia  and  observe  normal  movement. 
Allow  the   chloroform   gas  to  flow  fcr  a  moment 


22  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

into  the  cell.      Note  the   effect  of  chloroform  upon 

ciliary  activity. 
(5)   How  many  times  may  the  cilia  be  narcotized  with 

chloroform   and  revived  again  through  ventilation  ? 
{6)   Repeat  (4)  with  ether  in  place  of  chloroform. 
(7)   Repeat  (5)  with  ether  in  place  of  chloroform. 
c.      Determine  the  action  of  alcohol  vapor  upon  cilia. 


II.    To  determine  the  amount  of  work  done  by  cilia. 

/.  Appliances. — Physiological  operating  case  ;  frog  board  ; 
cork  board  10  cm.  long  by  5  wide;  a  centimeter  rule; 
a  block  of  wood  4  or  5  cm.  in  height  ;  a  bit  of  sheet 
lead  1  mm.  thick;  scales  correct  to  a  milligram  should 
be  accessible  to  the  student. 

2.  Preparation. — Pith  a  frog  and  destroy  cord.  Dissect 
out  oesophagus  and  stomach  as  directed  in  lesson  I. 
Fix  to  cork  board  so  that  the  long  axis  of  the  cesoph 
agus  shall  be  parallel  with  the  long  axis  of  the  board. 
Cut  a  piece  of  sheet  lead  just  5  mm.  square  and 
another  3  mm.  square.      Weigh  each  of  them. 

j.  Operation. — Wash  off  ciliated  surface,  remove  the  sur- 
plus moisture  with  filter  paper,  and  place  the  lead 
gently  upon  the  anterior  end  of  the  oesophagus. 

The  incline  of  the  ciliated  surface  may  be  changed 
by  resting  it,  at  different  angles,  against  the  block  of 
wood  as  shown  in  Fig.  2. 

4.    Observations. 

(1)  If  the  preparation  is  successful  the  piece  of  metal 
will  be  slowly  carried  up  the  incline.  Should  it  fail 
a  thinner  piece  of  lead  or  a  new  preparation  may 
succeed.  With  a  given  incline,  is  the  small  piece  of 
lead  carried  more  rapidly  than  the  large  piece? 

(2)  If  W=work  done,  g  =  weightin  milligrams  and 
li  —  height  in  millimeters,  then  W  =  g  X  h 
would  give  the  work  in  milligram-millimeters. 

(3)  Determine  the  distance  through  which  the  weight 
is  carried   in  a  unit   of  time    [one   minute   is  a  con- 

23 


■II 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


venient   unit   of  time    to  use],  when    the    incline   is 
placed  as  shown  in  the  figure. 

(4)  With  the  apparatus  so  adjusted  what  is  the  value 
of  h  when  the  distance  which  the  weight  moves  is  1 
cm.  ? 

Does  the  thickness  of  the  cork  board  need  to  be  con- 
sidered ? 

(5)  What  is  the  work  per  minute,  expressed  in  milli- 
gramm-millimeters  ? 


Fig.  2. 

Fig.  2.      Appliances   for    changing    the    angle  of   inclination    of    the 
ciliated  tissue. 

(6)  What  is  the  work  done  expressed  in  ergs? 
[1  erg  =  1  dyne  X  1  centimeter;  1  dyne  =  1  gramme 
+  981] 

(7)  Using  the  same  incline  compare  the  result  in 
work  done  per  minute  with  the  two  different  weights? 
Account  for  the  results  ? 

(8)  Using  the  weight  which  gave  the  larger  values  in 
the  foregoing  experiments,  find  the  degree  of  in- 
cline which  will  yield  the  greatest  amount  of  work  ? 


GENERAL  PHYSIOLOGY.  25 

(9)  What  significance  has  the  variation  of  the  thick- 
ness of  the  lead  weight  ?  Determine  the  upper 
limit  of  thickness? 

(10)  Would  it  be  possible  to  determine  the  amount 
of  work  accomplished  by  each  cilium  ?  By  each 
stroke  of  a  cilium  ? 


B.     THE  GENERAL    PHYSIOLOGY   OF   MUSCLE   AND 
NERYE  TISSUE. 


III.  Demonstration:  a,  Elements  and  conductors;  b,  Keys; 

c,  The  commutator;  d,  Work  done ;  e,  Elec= 

trical  units. 

The  function  of  muscle  tissue  is  to  contract.  Skeletal 
muscles  contract  only  in  response  to  stimuli.  Stimuli  may 
act  upon  the  muscle  tissue — direct  stimulation — or  upon 
the  motor  nerve  which  supplies  the  muscle — indirect  stimu- 
lation. To  study  the  functions  of  muscle  and  nerve  tissue 
one  requires  to  have  at  command  various  methods  of  stim- 
ulation. It  is  usual  to  apply  mechanical,  thermal, 
chemical  and  electrical  stimulation.  Experience  has 
shown  that  of  all  these  means  electricity  is  the  most  valu- 
able, because  it  is  subject  to  the  greatest  number  of  varia- 
tions in  strength  and  in  method  of  application.  Before 
entering  upon  a  study  of  the  responses  of  irritable  tissues 
to  electrical  stimuli  it  is  essential  to  make  a  short  study 
of  the  appliances  used.  As  many  of  these  appliances 
have  been  used  by  the  student  in  the  physical  laboratory 
it  will  be  taken  for  granted  that  he  is  familiar  with  the 
principles  involved  in  their  use. 

/.  Appliances. — 2  Daniell  elements  or  cells;  wires;  contact 
key;  Du  Bois  Reymond  key;  mercury  key;   commuta- 

26 


GENERAL  PHYSIOLOGY.  27 

tor;  sulphuric  acid,10f/f;  copper  sulphate,  saturated 
solution;  mercury. 
Experiments  and  Observations. 
a.  The  Daniell  cell. — Present  the  four  parts  of  the 
cell.  Half  fill  the  outer  receptable  of  the  cell  with  the 
saturated  copper  sulphate  solution.  Put  the  copper 
plate  into  the  cell;  half  fill  the  porous  cup  with  the 
dilute  sulphuric  acid,  lower  the  zinc  plate  carefully 
into  the  cup.  The  plate  is  of  commercial  zinc  with 
its  various  impurities. 

(1)  Observe  the  vigorous  chemical  action  in  porous 
cup.  Write  the  reaction.  It  is  evident  that  the 
zinc  will  be  quickly  consumed  if  allowed  to  re- 
main in  the  acid  and  this  will  be  the  case  whether 
or  not  the  cup  and  zinc  plate  be  made  a  part  of 
an  electric  cell,  and  whether  the  cell  be  acting  or 
resting. 

(2)  The  amalgamation  of  the  zine.  [See  also  App. 
A. -4.]  Lift  the  zinc  plate  out  of  the  acid,  dip  it 
into  the  mercury.  The  mercury  adheres  to  the 
zinc,  mingles  with  the  surface  layer  of  zinc,  form- 
ing an  alloy,  with  a  brush  or  an  old  cloth  one 
may  rub  the  mercury  over  the  whole  surface  of 
the  zinc  plate — the  zinc  is  amalgamated.  The 
impurities  of  the  zinc  do  not  enter  into  the  alloy. 
In  this  way  only  the  pure  zinc  which  forms  a  part 
of  the  alloy  is  presented  to  the  acid.  Chemically 
pure  zinc  is  acted  upon  very  slowly  by  10% 
sulphuric  acid;  join  a  wire  to  the  exposed  end  of 
each  plate.  Touch  the  tongue  with  the  freed  end 
of  each  wire  separately;  touch  the  tongue  with 
both  wires  simultaneously.      Record  results. 

(3)   Place    the  porous  cup    with  the   zinc   plate   in  the 
receptacle    holding    the    CuS04    with    the    copper 


28  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

plate.  Touch  the  tongue  with  one  wire,  then  with 
the  other.  Touch  the  tongue  with  both  at  once. 
Bring  the  two  free  ends  of  the  wires  into  contact 
with  the  binding  posts  of  a  detector;  note  results. 
Touch  the  ends  of  the  wires  together,  if  the  condi- 
tions are  favorable  a  minute  spark  may  be  seen 
on  touching  and  on  separating  the  two  poles.  What 
conclusions  are  to  be  drawn? 
(4)  Define  element  or  cell  as  used  in  this  connection  . 
Define  plate,  pole,  electrode.  The  zinc  is  arbitra- 
rily taken  as  the  positive  plate  and  the  copper  as 
the  negative  plate.  The  pole  which  is  attached 
to  the  negative  plate  is  the  positive  pole,  and  that 
which  is  attached  to  the  positive  plate  is  the  nega- 
tive pole.  The  positive  pole  or  electrode  of  a  gal- 
vanic cell  or  of  a  battery  is  called  the  anode,  while 
the  negative  pole  or  electrode  of  a  cell  or  of  a  bat- 
tery is  called  the  kathode. 

b.  Keys. — (1)  Show  and  describe  the  simple  contact 
key  (Fig.  V-k),  the  mercury  key  (Fig.  3),  and  the  Du 
Bois-Reymond  key  (Fig.  4). 

(2)  Two   ways  of  using   the   Du   Bois  Reymond   key. 
1st.    As  a  simple  contact  key  (PI.  I  Fig  1.) 
2d.  As  a  short  circuiting  key  (PI.  I  Fig.   2.) 

c.  The  commutator. — Most  convenient  for  the  physio- 
logical laboratory  is  Pohl's  commutator  (Fig.  5). 
This  instrument  may  be  used  for  the  following  pur- 
poses: 

(1)  To  change  the  direction  of  the  current.  Set 
up  apparatus  with  cross  bars  in  place  as 
shown  in  PI.  I  Fig.  3.  Which  is  the  anode 
when  the  bridge  is  turned  toward  a  b?  Which 
is  the  anode  when  the  bridge  is  turned  toward 
c  d? 


GENERAL  PI  I J  'SIOL  OG  V. 


29 


(2)  To  change  the  course  of  the  current.  Set  up 
apparatus  with  cross  bars  removed,  as  shown 
in  PI.  I  Fig.  4.  What  course  will  the  current 
take  when  the  bridge  is  turned  toward  a,  b  ? 
What  course  when  the  bridge  is  turned  toward 
c,  d? 

(3)  Pohl's  commutator  may  be  used  as  a  simple 
mercury  key  (PI.  I  Fig.  5).     Is  the  current  open 


Fig.  3.  FlG.  4 

Fig.  3.     The  mercury  key.  Fig.  4.     The  DuBois- 

Reymond  key. 
or  closed  when  the  commutator  bridge  is  turned 
toward  a?     How  may  the  current  be  opened  or 
broken  ? 
d.  Work  done  by  the  cell — The  experiments  performed 
show  that  the  galvanic  cell  may  under  proper  con- 
ditions, liberate  energy.    This  energy  is  called  elec 
tricity.     But  the  immediate  source  of  the  particular 


80  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

electric  energy  liberated  in  the  foregoing  experi- 
ments is  the  latent  chemical  energy  represented  in 
the  plates  and  liquids  of  the  cell. 

Under  the  conditions  produced  in  the  working 
galvanic  cell  the  latent  chemical  energy  is  trans- 
formed, and  at  the  same  time  liberated  as  electric 
energy.  This  liberated  electric  energy  may  make 
itself  manifest  in  the  contact  spark,  in  moving  the 
detector  needle  or  in  lifting  the  armature  of  a  mag- 
net. In  the  last  case  mentioned  it  would  not  be 
difficult  to  determine  the  amount  of  work  done, 
though  it  might  be  somewhat  difficult  to  determine 
the  amount  of  work  which  a  cell  is  capable  of  per- 


Fig  5. 
Fig.  5.     Pohl's  commutator.     For  description  and  uses  see  III=C. 

forming  in  a  given  time.  If  one  were  to  weigh  the 
copper  plate  before  and  after  using  the  cell,  one 
would  find  that  it  had  increased  in  weight.  This 
increase  in  weight  is  an  index  of  the  amount  of 
chemical  action  in  the  cell  —  of  the  latent  chemical 
energy  which  has  been  transformed  into  electric 
energy.  It  must  be,  then,  at  least  an  approximate 
index  of  the  electric  energy  liberated.  An  exact 
index  of  the  amount  of  current  is  afforded  by  the 
amount  of  electrolysis.  For  example,  if  the  nega 
tive  pole  of  a  cell  be  attached  to  a  silver  or  platinum 


GENERAL  PHYSIOLOGY.  31 

Cup  containing  pure  nitrate  of  silver,  and  the  posi- 
tive pole  be  attached  to  a  piece  of  pure  silver  which 
is  immersed  in  the  silver  nitrate  solution,  it  will  be 
found  that  one  ampere  of  current  will  uniformly  de- 
posit 0.001118  gm.   of  silver    upon   the  cup  in  one 
second  of  time.      This  brings  us  to  the  question  of 
the  units  of  electrical  measurements. 
e.   Electrical  units. — The  electrical  energy  available  at 
any  point  in  a  circuit,  i.  e.,  the  current,  as  it  is  called, 
is,    according   to  Ohm's  law,  equal  to  the  liberated 
energy— the    electromotive    force — divided    by    the 
total  resistance  of  the  circuit.     This  is  expressed  in 
Ohm's    formula,   C  =  ?^LX-       C  =  |        It    is    im- 
possible for  the  physicist  to  make  any  progress  in 
the    study  of    electrical    energy  without    arbitrarily 
assuming    units    of    measurement    for    current,    for 
electromotive  force  and  for  resistance. 
^1)   Current  is  measured  in  amperes.     A  current  of 
one  ampere  deposits  upon  the  negative  electrode 
of  a  galvanic  cell  or  battery  0.001118  gm.  of  silver 
per  second,  or  4.025  gm.  per  hour.     [See  above  ] 
A  concrete  idea  of  the  ampere  may  be  gained 
from    the  fact    that    the  small  sized    Daniell  cell 
produces  a  current  of  about  %  ampere  when  the 
external  resistance  is  reduced  to  a  minimum. 
(S)   Resistance    is    measured    in    ohms.      An    ohm    is 
that  amount  of  resistance,  opposed  to  the  trans- 
mission of  electrical  energy,  by  a  column  of  mer- 
cury  1    sq.    mm.  in  cross   section  and   106.3   cm. 
in    length.      For    general    purposes    an    ohm    re- 
sistance   is    that    of    a    pure    silver    wire    1    mm. 
in  diameter  and  1  meter  in  length. 
(3)   Electromotive  force  is  measured  in  volts. 

A  volt  is  that  amount  of  electrical  energy  which 


32  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

will  produce  1  ampere  of  current  after  overcom- 
ing 1  ohm  of  resistance. 

"  The  ohm,  the  ampere  and  the  volt  are  thus  closely 
related,  and  if  any  two  of  them  be  known  with  ref- 
erence to  any  particular  electric  circuit  or  portion 
of  a  circuit  the  value  of  the  third  may  be  readily 
inferred."— [Daniell].  For  if  C  =  |  then  E  =  CxR 
and  R  =  7y  Tne  same  relations  may  be  expressed  thus: 
1  ampere  current^    'To1'"' F"     or  1  ampere^011 

r  1  Ohm  Resistance.  ^  lOum 

Therefore  (1)  Volts  =  AmperesxOhms. 

(2)  Amperes  =  Volts-s-Ohms, 

(3)  Ohms  =  Volts-*-Amperes. 

The  small  Daniell  cell  has  about  1  volt  E.  M.  F. 
and  4  ohms  resistance,  the  current  from  such  a  cell 
is  then  equal  to  approximately  ^  ampere. 

There  are  numerous  other  units  of  measurement 
used  by  physicists  and  electricians,  but  for  our  pur- 
pose it  is  not  necessary  to  review  these  more 
specialized  points. 


GENERAL  PHYSIOLOGY. 


33 


z   fz 


IV.     Demonstration :     Batteries. 

A  battery  is  a  group  of  two  or  more  elements  or  cells 
arranged  to  produce  increased  or  multiple  effect.  If  one 
wishes  to  use  a  stronger  current  than  that  afforded  by  one 
cell,  his  first  thought  is  to  increase  the  number  of  cells,  or 
to  procure  a  larger  cell.  Experimentation  will  show  him 
that  it  is  not  a  matter  of  indifference  which  of  these  courses 
to  pursue.  In  the  first  place  if  he  attempts  to  satisfy  the 
conditions  he  will  find  that  to  increase  the  size  of  the  cell 
increases  the  current  only  when  the  external  resistance  is 
relatively  small,  and  furthermore,  there  are  practical  limi- 
tations to  the  size  of  a  cell  and  these  may  be  much  within 
the  requirement  which  the  cells  must  satisfy.  It  be- 
comes apparent,  then,  that  he  who  would  use  electrical 
energy  beyond  the  most  limited  field  must  resort  to  a  bat- 
tery composed  of  a  number  of  cells.  The  problem  which 
first  confronts  him  is,  how  shall  these  cells  be  arranged 
/.  Appliances. — 6  Daniel  cells;  wires;  detector,  (Fig.  0) 
composed  of  simple  magnetic  needle  mounted  over 
circle  divided  into  degrees;  rheostat  or  resistance  box, 
representing  at  least  100  ohms. 
2.  Experiments  and  Observations. 

(1)  (a.)  Join  up  apparatus  as  shown  in  PL  I.,  Fig.  6. 
With  the  plugs  all  fixed  in  the  rheostat,  i.  e., 
with  no  resistance  except  that  of  the  wires  and 
battery,  and  the  indicator  needle  at  0°,  open 
the  key  and  then  observe  the  angle  at  which 
the  needle  comes  to  rest. 
(p.)  Remove  from  the  rheostat  the  plug  which  will 
throw  into  the  circuit  an  extra  resistance  of  10 
34 


GENERAL  PHYSIOLOGY. 


35 


ohms       Allow  the  needle   to  come  to   rest  and 
note  angle? 
(V.)  Remove  from    the    rheostat    plugs    which   will 
represent  in  the  aggregate   100    ohms  of  extra 
resistance.     Note  angle  of   indicator  as  before. 
(2)  Join  up  two  cells  in  multiple  arc  as  shown  in  PI.  I., 
Fig,  1.     That  is,  join  both  copper  plates   to  one 
copper    wire    and    both    zinc    plates    to    another. 
These  wires  are  to  be  carried  to  key,  rheostat  and 
detector  as  shown  in  PI.  I.,  Fig.  6. 
{a.)  Note  angle  of  needle  with  no   extra  resistance. 
(b. )   Note  angle  with   10  ohms  extra  resistance. 
(c.)   Note  angle  with  100  ohms  extra  resistance. 


Fig.  6. 

Fig.  6.  Detector,  composed  of  simple  magnetic  needle  mounted 
over  a  graduated  circle.  The  two  heavy,  copper  wires  which  encircle 
the  compass  offer  slight  resistance  to  the  electric  current. 

(3)  Join  up  four  cells  in  multiple  arc  or  "abreast"  and 
repeat  the  observations  of  angle  at  the  three  re- 
sistances as  above. 

(  4  )  Join  up  six  cells  in  multiple  arc  and  repeat  observa- 
tions with  0X2,  10/2,  and  100i2  resistance. 

(5)  Join  up  two  cells  in  series  as  shown  in  PI.  I.,  Fig. 
8.  That  is,  join  the  copper  of  the  first  cell  to  the 
zinc  of  the  second.  The  first  cell  will  have  a  zinc 
uncoupled    and   the    second    will    have  a  copper 


36  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

plate  uncoupled.  These  two  uncoupled  terminal 
plates  of  the  battery  are  the  ones  from  which  to 
lead  off  the  wires  to  the  other  apparatus,  which 
should  be  arranged  as  shown  in  PI.  I.,  Fig.  6. 
Repeat  the  observations  on  the  angle  of  deviation 
of  the  needle,  using  the  0£1,  lOfl  and  100.fi 
resistance  as  above. 
I  6)  Join  up  four  cells  tandem  or  in  series,  and  repeat 
the  three  observations. 

(7)  Join  up  six  cells  in  series  and   repeat   observations. 

(8)  Tabulate  results  and  draw  conclusions. 

1.  There  is  a  marked  difference  in  the  results  of  the 
two  methods. 

2.  With  low  external  or  circuit  resistance  the  current 
as  indicated  by  the  angle  at  which  the  detector  needle  stood 
increased  with  an  increase  in  the  number  of  cells  joined  in 
multiple  arc  or  abreast. 

3.  With  high  external  resistance  the  strength  of  the 
current  does  not  seem  to  be  essentially  increased  by  in- 
creasing the  number  of  cells  joined  up  abreast. 

4.  With  low  external  resistance  the  strength  of  the 
current  is  not  increased  by  adding  cells  in  series. 

5.  With  high  external  resistance  the  strength  of  current 
increases  with  an  increase  in  the  number  of  cells  joined 
up  in  series  or  tandem. 

The  following  theoretical  points  are  worthy  of  note  : 

The  general  formula   C  =  g   does    not    differentiate   le 

tween  that  part  of  the  resistance  furnished  by  the  battery 

and    that    part    furnished    by    the    external    circuit.     The 

former   is   called   internal   resistance  (ri)  and  the  latter  is 

called      external      resistance     (re).      So     we     may     write 

R  =  ri  +  re  and  C  =~ — 
1  ri+re  • 


GENERAL  PIIYS/OLOGY.  37 

Case  I. 

Suppose    that    the    external  resistance    is    so  great   in 

comparison  with  the  internal  resistance  that  the  latter  may 

be  made  equal  to  zero  (ri  =  0)  C'=— -^ —  =  —  for  one  cell. 
^  v  J  n+re  re 

Suppose  that  we  arrange  a  battery  of  sixteen  cells  in 
multiple  arc.  Experiment  has  shown  that  when  a  battery 
is  so  arranged  the  internal  resistance  of  the  battery  de- 
creases in  proportion  to  the  number  of  cells  and  that  join- 
ing up  cells  in  multiple  arc  is  equivalent  to  simply  increas- 
ing the  size  of  the  plates. 

Our  formula  then  becomes  : 


C'=iA-  :  but_EL=0;C'=_E_;  C=C 

£L+re  16  re 

Therefore  no  advantage  is  gained  by  joining  up  cells 
in  multiple  arc  when  the  external  resistance  is  incompara- 
bly greater  than  the  internal  resistance. 

Case  II. 

Let  the  internal  resistance  be  incomparably  greater 
than  the  external. 

Then  for  one  cell:  C  =^^;  but  re  =  0,  therefore  C  =  -^- 
Join  up  16  cells  in  multiple   arc.     The  internal  resist- 
ance is  thus  decreased  by  the  factor  16. 

C'=  7r^—  ;  re  =  0;  therefore  C'=JL  =  1-|?;C=16C. 

f6  +  re  T6~ 

Therefore  when  the  internal  resistance  is  incomparably 
greater  than  the  external  resistance  the  current  increases 
proportional  with  the  number  of  cells  joined  in  multiple 
arc. 

Case  III. 

Let  the  internal  resistance  be  so  small  relatively  as  to 
be    discarded.     For  one  cell  C 


E  E 


ri+re  re 


38  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

Join  up  16  cells  in  series.  Experiment  has  shown 
that  when  cells  are  joined  in  series  the  internal  resistance 
increases  in  proportion  to  the  number  of  cells,  for  the 
current  must  pass  through  all  of  the  cells  ;  further,  the 
electromotive  force  is  reinforced  as  it  passes  through  each 
cell  so  that  it  also  increases  in  proportion  to  the  number  of 
cells.     Our  formula  then  would  be  : 

C'=  .    "*       but    ri  =  0;  therefore,  C'=^;  C=16C. 
lbn+re  >  '  '  re  ' 

Therefore  the  current  will  increase  in  proportion  to  the 
number  of  cells  joined  in  series,  when  the  external  resist- 
ance is  incomparably  greater  than  the  internal  resistance. 

Case    IV. 

Let  the  internal  resistance  be  incomparably  greater 
than  the  external  and  join  16  cells  in  series,  then  : 

C'=   1cl6,i      j  but   re  =  0;    therefore  C'=  ~r  =   4". 
16  n+re    '  '  16  n  ri 

In    this   case,  however,  C— — :  therefore  there  is  no  ad- 
'  '  ri' 

vantage   gained  by  increasing  the  number  of  cells  in  series 
when  the  external  resistance  is  very  small. 

Case  V. 

Practically,  however,  one  deals  with  cases  where 
neither  the  external  nor  the  internal  resistance  is  so 
small  as  to  be  ignored.  Let  us  suppose  that  we  have  a 
battery  of  a  cells,  that  the  internal  resistance  of  each  cell 
is  r  and  that  the  total  external  resistance  is  R.  It 
has  been  shown  experimentally  that  the  current  is  great- 
est when  the  external  resistance  is  equal  to  the  internal 
resistance;  i.  e.,  when  —  =  R;  s  being  the  number  of 
cells  in  series  and  m  the  number  in  multiple  arc. 


GENERAL  PHYSIOLOGY.  30 

We  have,  then,  two  equations. 

(2)   s  m  =  a 

Find  s  and  m. 

(s)  «  =  -£■ 

(4)  s  =    =» 

(5)  -i  =    =L»;  or  a  r,  =  m  2R. 

(6)  m    =    Vir"j  or»  in  a  similar  way, 
(6')   s    =    V^- 

Let  us  take  a  concrete  case,  using  our  16  cells,  each  of 
which  has  an  internal  resistance  of  4  ohms,  how  shall  we 
arrange  them  to  get  the  best  results  with  16  ohms  external 
resistance. 

™  —    /ar     —    /16><4     —    o 

s    =    ^    =  ^16X16   =   g 

We  shall  therefore  arrange  the  battery  in  a  series  of  8 
pairs,  each  pair  being  joined  abreast. 

How  must  they  be  arranged  when  there  are  64  ohms  or 
more  of  external  resistance? 

How  must  they  be  arranged  when  there  are  only  4 
ohms  of  externa'  resistance? 

What  arrangement  would  you  adopt  if  there  is  only  1 
ohm  external  resistance? 


V.     Demonstration:    Methods  of    varying   the    strength 

of  current,     a.     The  rheostat,     b.     The 

Du  Bois=Reymond  rheocord. 

It  has  already  been  shown  that  the  strength  of  current 
may  be  varied  by  increasing  the  number  of  cells  or  by 
changing  their  arrangement  in  the  battery.  This  method 
is  indispensable,  but  it  has  its  limitations.  If  one  has  a 
small  cell  and  wishes  to  decrease  the  current,  he  must 
have  recourse  to  another  method.  From  the  formula  C  = 
-jj-  it  is  evident  that  one  may  decrease  the  current  by  in- 
creasing the  resistance. 
a.     The  rheostat. 

1.  Appliances. — Resistance  box  or  rheostat;   1  cell;  5  wires; 

detector. 

2.  Experimetits  and  Observations. 

(I)  Set  up  the  apparatus  as  shown  in  PI.  I.,  Fig.  6. 

(1)  With  plugs  all  fixed  in  rheostat,  needle  of  detec- 
tor at  0°,  close  key  and  note  angle  of  deviation. 

(2)  Remove  the  plug  which  will  throw  into  the  circuit 
the  lowest  resistance  contained  in  the  rheostat. 
Note  the  angle. 

(3)  Add  to  the  above  resistance  the  smallest  possible 
increment  and  note  angle. 

(4)  Proceed  in  this  way  tabulating  results. 

(5)  Conclusions. 

(II)  Another  method  of  using  the  rheostat.  The  rhe- 
ostat maybe  used  in  short  circuit  as  shown  in  PI.  I.,  Fig. 
9.  From  this  arrangement  of  the  apparatus  it  is  appar- 
ent that  when  all  of  the  plugs  are  in  place  the  current 
will  be  short  circuited  by  the  rheostat.  If  the  resist- 
ance of  that  part  of  the  circuit  leading  to  the  detector 
— the   long    circuit — be    considerable  the  long  circuit 

40 


GENERAL  PHYSIOLOGY  41 

current  will  probably  not  be  sufficient  to  cause  any 
deviation  of  the  detector  needle;  for  the  current  varies 
inversely  as  the  resistance  (C  x  -pr)>  and  if  the  re- 
sistance of  the  long  circuit  (Rj  be  incomparably 
greater  than  the  resistance  of  the  short  circuit  (R'), 
then  the  current  of  the  long  circuit  (C)  will  be  incom- 
parably less  than  the  current  of  the  short  circuit  (C')( 
i.e,C:C'::{  =  -^-,  or  C  :  C  ::  R'  :  R;  therefore  if 
R'  =  0,  C  must  equal  0. 

Suppose  that  the  resistance  of  the  detector  circuit 
be  only  10  ohms,  and  suppose  we  remove  from  the 
rheostat  plug  that  represents  0.1  ohm  resistance,  then 
one-hundredth  of  the  current  will  pass  through  the 
detector.  If  we  make  the  resistance  in  the  short  cir- 
cuit 0.2  ohms  then  one-fiftieth  of  the  current  will  flow 
through  the  long  circuit. 

In  this  way  we  may  increase  the  detector  current 
step  by  step  until  the  maximum  is  reached.  What 
is  the  maximum  current  to  be  derived  when  the 
resistance  in  the  long  circuit  equals  10  ohms,  the  maxi- 
mum resistance  of  the  rheostat  100  ohms,  external  re- 
sistance in  circuit  between  cell  and  rheostat  1  ohm, 
E.  M.  F.  =  1  volt,  internal  resistance  of  cell  four 
ohms  ? 
The  Du  Bois=Reymond  Rheocord. 

In  the  use  of  the  rheostat  the  variation  of  the  cur- 
rent is  step  by  step  and  not  gradual.  Experience  has 
shown  that  tor  certain  physiological  experiments  it  is 
necssary  to  cause  a  gradual  variation  of  the  current, 
i.  e.,  an  increase  by  infinitessimal  increments.  The 
Du  Bois-Reymond  rheocord  is  an  instrument  which 
fulfills  this  condition  by  adding  to  the  short  circuit 
millimeter  by  millimeter  the  resistance  of  a  platinum 
wire.     The  principle  and  use  of  the  Du  Bois-Reymond 


42  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

rheocord  is  the  same  as  that  of  the  rheostat  with  the 
exception  that  one  ohm  resistance  is  furnished  by  two 
platinum  wires  which  are  stretched  along  the  top 
of  the  long  resistance  box.  A  mercury  bridge 
makes  electric  connection  between  these  wires.  When 
the  bridge  or  "  slider  "  stands  at  0  the  conditions  are 
the  same  as  one  has  in  the  use  of  the  rheostat  with  all 
of  the  plugs  in.  As  the  bridge  is  moved  gradually 
from  0  to  100,  one  ohm  of  resistance  is  as  gradually 
thrown  into  the  short  circuit.  At  that  point  a  plug 
representing  one  ohm  resistance  may  be  removed  and 
the  bridge  brought  back  to  0,  and  another  ohm  of  re- 
sistance gradually  introduced  into  the  short  circuit. 
In  this  way  any  desired  amount  of  resistance  may  be 
introduced  by  infinitely  small  steps — by  infinitessimal 
increments— and  the  current  of  the  long  circuit  will 
be  increased  correspondingly. 

/.  Appliances.  —  1  cell;  Du  B-R.  Rheocord;  detector;  5 
wires;  key. 

2.   Experiments  and  observations. 

(1)  Set  up  apparatus  as  shown  in  PI.  II,  Fig.  1. 
With  bridge  at  0,  close  key  and  note  angle. 

(2)  Leaving  the  key  closed  gradually  slide  the  bridge 
to  1,  then  slowly  and  with  an  even  rate  of  motion 
on  to  100,  noting  the  behavior  of  the  detector  needle. 

(3)  Open  the  key,  remove  the  plug  which  represents 
1  ohm,  and  slide  the  bridge  back  to  the  zero  position, 
close  the  key  and  note  the  angle  at  which  the  needle 
comes  to  rest.  If  the  resistance  of  the  platinum 
wires  is  1  ohm  then  the  needle  will  come  to  rest  at 
the  same  point  noted  above  when  the  bridge  stood 
at    100. 

(4)  From  this  point  the  needle  may  be  caused,  by 
sliding  the  bridge  from  0  to  100,  to  gradually  in- 
increase  its  angle. 


VI.     Demonstration:      To    vary    the    current    through 

the  use  of  (a.)  the  simple  rheocord,  or  (b.) 

the  Ludwig  compensator. 

Besides    the    methods   already    used    for    varying    the 
strength  of  the  current  one  may  use  the  derived  current. 

The    simple    rheocord  (Fig.    7)  may   be  used   for   this 
purpose. 

a.     The  simple  rheocord. 

/    Appliances. — One  or  more  cells;  simple  rheocord;  5  wires; 
detector. 


Fig.  7. 
Fig.  7.     The  simple  rheocord.     See  also  PI.  II,  Fig.  2. 

2.   Experiments  and  observations. 

(1)  set  up  the  apparatus  as  shown  in  Fig.  2,  Plate  II. 
From  the  figure  we  see  that  from  the  cell  to  post 
A,  thence  through  the  German  silver  wire  to  postB 
and  back  to  the  cell  makes  a  complete  circuit.  Hav- 
ing reached  the  metallic  slider  (S)  the  circuit  has 
two  paths  presented.  1st,  from  S  direct  to  B;  2d, 
43 


44  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

from  S  through  D  and  back  to  B.  The  total  cur- 
rent is  divided  into  two  parts,  C  which  passes 
along  the  wire  from  S  to  B,  and  C  the  derived  cur- 
rent which  passes  through  the  detector.  Sup- 
pose the  resistance  to  the  last  named  current  is  R' 
and  that  to  the  direct  current  is  R,  the  relative 
strength  of  these  two  currents  is  expressed  in  the 
following  proportion:   C  :  C  :  ;  R  :  R'. 

But  the  resistance  of  the  German  silver  wire  may 
be  conveniently  divided  into  100  equal  parts  (100  r). 

If  the  slider  be  placed  at  any  position  along  the 
wire,  say  at  x  centimeters  from  the  end,  then  the 
formula  would   be  C  :  C  :  :  lOOr—  xr  :  R'. 


C 


_     Cr(lGO-x) 


R 

Suppose  that  R  =  1  ohm  (r  =  0.01  ohm);  R'  = 
2  ohms  and  x  =  0;  i.  e.,  suppose  the  slider  to  be 
hard  up  to  A,  then  C  =  Cr(^00~x)  =  -§-  J  or  the 
current  which  passes  to  the  detector  is  one-half  as 
strong  as  the  current  through  the  rheocord. 

(2)  What  is  the  relative  strength  of  the  two  currents 
when  x  =  10? 

(3)  What  is  the  relative  strength  of  the  two  currents 
when  x  =  50? 

(4)  What  is  the  relation  of  C  to  C  when  x  =  99? 

(5)  What  is  the  relation  of  C  to  C  when  x  =  100? 
From  this  course  of  reasoning  it  is  evident  that 

in  the  simple  rheocord  we  have  an  instrument  with 
which  we  can  vary  a  derived  current  from  zero  to  a 
maximum.  Just  what  the  value  of  this  derived  cur- 
rant will  be  will  depend  upon  the  voltage  of  the  cell 
or  battery  and  the  total  resistance  to  be  overcome, 
as  well  as  upon  the  distribution  of  that  resistance. 

(6)  Verify  the  theory  just  developed,   making  out  a 
table  of  detector  readings. 


GENERA L  PH ) 'SIOL OGY. 

"If 


45 


Plate  II 


46 


LAB  OR  A  TOR  Y  G  U1DE  IN  Pll  YSIOL  O  G  Y. 


The  Ludwig  compensator. 

This  instrument,  though  used  in  a  class  of  experi- 
ments quite  different  from  those  in  which  the  rheocord 
is  used,  involves  the  same  principle  as  that  involved 
in  the  simple  rheocord,  and  is  used  to  make  minute 
variation  in  the  strength  of  a  current.  The  general 
construction  of    the  instrument    is  shown    in    Fig.  8. 


Fig.  8.  The  Ludwig 
compensator,  originally 
devised  by  Ludwig  to 
compensate  a  muscle 
current,  may  be  used 
in  the  same  way  as  the 
simple  rheocord.  Its 
maximum  current  is, 
however,  limited.  For 
description,   see    Vl=b. 


Fig.  8. 

The  outer  receptacle  is  of  copper  and  serves  as  the 
copper  plate;  within  is  a  porous  cup  containing  the 
zinc  plate.  This  is  practically  a  Daniell  cell.  A 
graduated  upright  of  brass  makes  metallic  contact 
with  the  copper  plate,  and  at  A  the  circuit  is  com- 
pleted by  a  platinum  wire  to  B. 


GENERAL  PHYSIOLOGY.  47 

A  slider  makes  contact  with  the  platinum  wire,  but 
slides  along  the  standard  by  an  ebonite  arm.  The 
derived  current  passing  along  the  wires  A  and  B,  and 
the  direct  current  from  S  to  B  along  the  platinum  wire 
sustain  a  relation  similar  to  that  of  currents  C  and  C 
in  the  rheocord. 

/.  Appliances. — Ludwig  compensator;    2    wires;    detector. 

2.    Theory,  experiments  and  observation. 

(1)  Join  the  two  poles,  a  and  b,  to  the  detector;  place 
the  slider  at  0  cm.,  or  hard  up  to  the  zinc  plate,  and 
note  the  deviation  of  the  needle. 

(2)  Gradually  move  the  slider  from  0  cm.  to  50  cm. 
(or  100)  noting  the  effect  upon  the  needle. 

(3)  Suppose  the  detector  circuit,  from  S  through  the 
detector  and  back  to  B,  has  a  resistance  of  10  ohms 
(R'  —  10).  Let  the  resistance  of  the  platinum  wire 
be  0.01  ohm  per  centimeter;  for  the  instrument 
figured,  R  =  0.5  ohm.  Let  C'  be  the  detector 
current,  and  C  the  direct  current.  Then  C  :  C  : : 
JL  :  i,  or  O :  C  : :  R  :  R',  or  C  =  ^P-  Let  x  be 
the  distance  in  centimeters  from  B  to  S,  or  the  read- 
ing of  the  position  of  the  slider;  then  the  proportion 
of  R  at  any  position  of  the  slider  would  be  -g^-. 
C'=  ^j*1;  substituting  the  assumed  values,   C'  =  -5-^-. 

(4)  When  x  =  0  how  much  current  will  flow  through 
the  detector? 

(5)  When  the  slider  stands  at  10  cm.  what  proportion 
of  the  total  current   will  flow  through  the   detector  ? 

(6)  When  the  slider  stands  at  25  cm.,  how  much 
larger  is  C  than  C? 

(1)  When  the  value  of  x  is  50  the  ratio  of  the  detector 

current  to  the  direct  current? 
(8)  Verify   all  of  these   theoretical   results   as   far   as 

possible,  by  experiment. 


VII.     Demonstration:    To  send  an  electric  current  into 
a  nerve  gradually.     Fleischl's  rheonom. 

When  one  studies  the  effects  of  thermal,  mechanical  or 
chemical  stimuli,  he  may  apply  the  mechanical  stimulus  so 
slowly  that  the  nerve  may  be  severed  without  calling  forth 
a  response;  he  may  apply  heat  to  the  fresh  nerve  so  grad- 
ually that  the  nerve  may  be  actually  cooked'  without  caus- 
ing a  contraction  of  the  muscle  which  it  supplies. 

The  problem  which  we  have  next  to  solve  is  to  apply 
an  electrical  stimulus  gradually. 

/.  Appliances. — Fleischl's  Rheonom;  1  Daniell  cell;  Du 
Bois-Reymond's  "Muscle  Telegraph;"  contact  key; 
detector;  saturated  solution  of  zinc  sulphate;  5  wires; 
frog;  operating  case. 

The  rheonom  is  constructed  as  shown  in  PI.  II. 
Fig.  3 — R.  Its  essential  features  are:  g,  the  non- 
conducting base  with  circular  groove;  s,  the  non- 
conducting rotatable,  central  standard;  P,  the  battery 
binding  post;-,  having  zinc  connection  with  the  groove; 
p,  the  rotating,  binding  posts,  having  zinc  limbs  con- 
necting with  the  groove. 
2.  Experiments  and  Observations.  —  Set  up  apparatus  as 
shown  in  PI.  II.  Fig.  3,  after  amalgamating  the  zinc 
tips  which  dip  into  the  zinc  sulphate.  Fill  the  groove 
with  zinc  sulphate. 

(1)  Find  and  mark  the  zero  position  for  the  rotating 
limbs  of  the  rheonom;  i.  e.,  find  the  position  which 
will  give  no  deviation  of  the  detector  needle  when 
the  contact  key  is  closed. 

48 


GENERAL  PHYSIOLOGY.  49 

(2)  Find  and  mark  the  position  which  the  rotating 
limbs  occupy  when  the  detector  needle  indicates  10°. 

(3)  Find  and  mark  in  succession  each  higher  incre 
ment  of  10°  until  the  maximum  is  reached. 

(4)  Rotate  the  limbs  so  gradually  as  to  cause  the  de- 
tector needle  to  rotate  with  slow  and  regular  motion 
from  the  zero  position  to  the  maximum  position  and 
back. 

(5)  Make  a  gastrocnemius  muscle  nerve  preparation; 
mount  it  in  the  muscle  telegraph;  change  the  wires 
from  the  detector  to  the  electrodes  of  the  muscle 
telegraph;  place  the  limbs  of  the  rheonom  in  the 
maximum  position,  close  the  key.  With  the  closing 
of  the  key  the  maximum  current  is  instantly  thrown 
into  the  nerve  and  serves  as  a  strong  stimulus  in 
response  to  which  the  muscle  contracts. 

(6)  Place  the  limbs  of  the  rheonom  in  the  minimum 
position.  Close  the  key.  Inasmuch  as  the  muscle 
nerve  preparation  is  much  more  sensitive  to  elec- 
tricity than  is  the  low  resistance  detector  the  muscle 
will  probably  respond  when  the  conditions  are  as 
above  indicated.  Theoretically  a  zero  point  exists. 
Practically  it  is  difficult  to  find  it  for  a  muscle- 
nerve  preparation.  The  finding  of  a  position  where 
there  is  no  response  on  closing  the  key  is  however  not 
essential  in  this  experiment. 

(7)  Keeping  the  key  closed,  slowly  rotate  the  limbs 
of  the  rheonom  from  the  minimum  position  to  the 
maximum  position.  If  the  conditions  are  favorable 
this  can  be  done  without  calling  forth  a  response. 

(8)  Without  opening  the  key,  slowly  rotate  the  limbs 
backward  from  the  maximum  to  the  minimum  posi- 
tion. One  may  thus  send  through  a  nerve  a  strong 
current   and   may  withdraw  the  same  without  caus- 


30  LAB  OR  A  TOR  Y  G  UIDE  IN  PHYSIOL  OG  Y. 

ing    a    contraction   of    the   muscle.      Keep   the   key 
closed. 
(9)  Quickly  rotate  the  limbs  from  minimum  to  maxi 
mum;   the   muscle   responds.       Quickly  rotate  from 
maximum  to  minimum;  the  muscle  responds. 

From  the  preceding  observations  one  may  con- 
clude that  response  to  electrical  stimulation  is  elic- 
ited not  by  the  simple  flow  of  an  electric  current 
through  the  irritable  tissues,  but  by  a  more  or  less 
sudden  change  in  the  strength  of  the  current.  The 
opening  and  closing  of  a  galvanic  current,  also  its 
sudden  increase  or  decrease,  serves  as  an  efficient 
stimulus,  while  the  gradual  increase  or  decrease  in  the 
strength  of  the  current  causes  no  response. 


VIII.     Demonstration :     To   determine   the    influence   of 
the  kathode  and  anode  poles. 

Many  of  the  phenomena  of  muscle-nerve  physiology 
were  inexplicable  until  a  difference  was  noted  (Von  Bezold 
18(50),  in  the  influence  of  the  anode  and  kathode.  This 
difference  in  the  influence  of  the  two  poles  may  be  best 
observed  by  use  of  the  sartorius  muscle  of  a  frog. 

1.  Appliances. — A  double  myograph  and   support;  record- 

ing drum;  Daniell  cell;  Pohl  commutator;  Du  Bois- 
Reymond  Key;  nonpolarizable  electrodes;  5  wires; 
electrode  clamp  and  support. 

2.  Preparation. 

(a)  Nonpolarizable  electrodes.— -The  Du  Bois-Reymond 
nonpolarizable  [N  P]  electrode  is  made  as  follows: 
(Fig.  9).  T.  Glass  tube  of  about  4  mm.  lumen.  Z. 
Zinc  rod  with  a  binding  screw  (B).  The  zinc 
rod  must  be  amalgamated  before  use  in  an  electrode. 
R.  Rubber  tube  clasping  both  glass  tube  and  zinc 
rod.  S.  Saturated  solution  of  sulphate  of  zinc,  in- 
troduced with  a  narrow  pointed  pipette.  C.  Kaolin 
plug,  made  by  working  china  clay  powder  into  a  stiff 
paste  with  normal  salt  solution. 

The  electrodes  should  be  filled  at  each  time  of  using, 
and  the  parts  may  be  "assembled  "  in  the  order  and  man- 
ner enumerated  in  the  description. 

(b)  The  Fleischl  brush  electrode  differs  from  the  fore- 
going in  substituting  the  brush  of  a  camel's  hair 
pencil  for  the  kaolin  plug.  This  variation  of  the 
N  P  electrode  is  somewhat  more  difficult  to  pre- 
pare, but  is  more  convenient  for  certain  uses. 

51 


52 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


(7)  If  one  has  not  the  zinc  rods  at  hand  he  may  readily 
prepare  an  efficient  N-P  electrode  as  follows:  1st. 
Take  5  cm.  of  No.  16  copper  wire,  make  one  end 
perfectly  clean  and  bright.  2d.  Dip  the  bright  end 
into  molten  c.  p.  zinc.  The  zinc  adheres  to  the 
wire,  and  if  the  dipping  be  repeated  two  or  three 
times  the  lower   1    centimeter  of   wire  will   have  a 


Fig.  9. 


Fig.  9.     Nonparizable  electrodes,  hand  electrode. 

The  Du  Bois-Reymond  N-P  electrodes,  shown  in  the  two  middle 
cuts,  are  described  in  the  text  VI1I=2  (a),  (c). 

The  Fleischl  brush  electrode,  mentioned  in  the  text  [2  (b)],  may  be 
prepared  by  setting  the  brush  in  stiff  kaolin  paste,  or  if  a  more  perma- 
nent electrode  is  desired,  in  plaster  of  Paris. 

A  plaster  of  Paris  pencil,  as  shown  in  the  lower  left  hand  cut,  may 
be  used  for  ordinary  work  with  the  constant  current. 

The  hand  electrode  shown  at  the  right,  is  used  with  an  induced 
current. 

thick  coating  of  zinc.     3d.   Take  a  glass  tube  10  cm. 
long,    and   with    a   4   mm.   lumen,    draw    it    in    the 


GENERAL  PHYSIOLOGY.  53 

middle   to   about    two-thirds   its  original    diameter, 
cut  it  into  two  such  as  shown  in  the  figure.     Before 
assembling  the  parts,  that  part  of  the  copper  wire 
not   covered    by   zinc,    excepting   the   tip    (t)    must 
be  painted  with  brunswick  black  or  any  varnish,  and 
the  zinc  must  be  amalgamated.    With  this  electrode, 
as    with    the    preceding,  zinc   sulphate,  kaolin  and 
NaCl  0.(5  per  cent  are  used.     The  part  C  in  these 
electrodes  may  be  held  in  a  clamp. 
d.   A  double  ?nyograph. 
A  most  efficient,  as  well  as  convenient  and  economical 
double   myograph  may  be  arranged  for  this  experiment  as 
indicated  in  Fig.  10. 

It  will  be  noticed  that  two  common  muscle  levers  such 
as  are  shown  in  Fig.  13,  are  used,  that  these  are  held  in 
position  by  common  clamps  and  heavy  support,  that  the 
upper  myograph  is  reversed  and  its  lever  counterpoised 
by  the  weight  (w),  that  between  the  two  myographs  a  small 
wooden  block — with  a  longitudinal  hole  for  the  loop  of 
thread  which  holds  the  muscle — is  held  by  a  clamp. 
J.    The  experiment. 

(1)  Curarize  a  frog.     (See  Appendix  A-5.) 

(2)  After  the  lapse  of  three  hours  or  more,  the  sartorius 
muscle  may  be  prepared  as  described  in  Lesson  X. 

(3)  Mount  the  preparation  by  passing  a  loop  of  coarse 
thread  through  the  hole  in  the  block  (b),  lift  the 
muscle  by  its  tendon  of  insertion,  pass  it  through  the 
loop,  draw  the  loop  gently  around  the  middle  of  the 
muscle  and  fix  by  making  a  single  knot  around  the 
screw  (s)  of  the  clamp.  The  fine  hooks  which  join 
the  muscle  to  the  levers  may  now  be  passed  through 
the  tendons,  and  the  proper  position  of  the  levers 
effected  by  an  adjustment  of  the  clamps.  The  non- 
polarizable  electrodes   may  be   clamped    between  two 


54 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


pieces   of    cork   and  held    by   an    extra   support.      A 
"universal"   clamp  holder  is  a  most   desirable   acces- 
sory to  this  apparatus. 
The  electrical   apparatus   should   be  set  up  as  shown  in 
PI.  II.,  Fig.  4. 
With  this  arrangement  either   electrode  e  or  electrode 
e'  may  be  made  the  anode,  the  experimenter  needing  only 
to  reverse  the  commutator  bridge  to  reverse  the  position 
of  anode  and  kathode. 


Fig.  10. 

Fig.  10.     Double  myograph.     Described  in  the  text 
under  VIII=3. 

The  recording  drum  or  kymograph  should  rotate 
rapidly.  The  recording  points  of  the  myograph  levers 
should  be  adjusted  so  that  the  point  of  the  upper  one 
touches  the  drum  vertically  over  the  point  of  the  lower 
one.  Adjust  the  time  marker  so  that  it  will  indicate  the 
time  of  making  and   breaking   the  circuit,  i.  e.,  so   that  it 


GENERAL  PHYSIOLOGY.  55 

will  record  on  the  drum  the  time  of  making  stimulus  and 
the  time  of  breaking  stimulus.  The  recording  point  of 
the  time  marker  should,  of  course,  be  in  the  same  vertical 
line  with  the  myograph  points.  The  moist  tips  of  the 
N-P  electrodes  should  be  so  adjusted  as  to  just  touch  the 
muscle  above  and  below  the  loops  of  thread. 

(1)  Close  the  key.     If  the  preparation   has  been  sue 
cessful,   the   half   of   the  muscle  in  contact   with   the 
kathode  pole  will  respond  before  the  other  one. 

(2)  Break  the  current.     The  anode  should  respond  first. 

(3)  Reverse  direction  of  current  and  repeat  (1)  and  (2). 

(4)  Vary  the  strength  of  current  through  use  of  simple 
rheocord  and  determine  whether  the  results  are  the 
same  for  currents  of  different  strength. 

Law  I.      The  make-contraction  starts  at  the  kathode  and  the 

break-contraction  starts  at  the  anode,  or 

When  irritable  tissue,  muscle,  or  nerve,  is  subjected  to  a 

galvanic  current  the  response  to  the   stimulation  begins  in 

the   region  of  the   kathode  on   making   the   current  and  in 

the  region  of  the  anode  on  breaking  the  current. 

Would  the  foregoing  observations  justify  the  following 
statements:  (1)  Kathcdic  contractions,  or  make  contrac- 
tions, may  be  caused  by  a  galvanic  current  which  is  too 
weak  to  cause  anodic  contractions  or  break  contraction. 
(2)  Kathodic  or  make  contractions  are  stronger  than 
anodic  or  break  contractions. 


IX.     a.     The    muscle  =  nerve     preparation,     b.    Indirect 

mechanical,  thermal  and  chemical  stimu= 

lation  of  the  gastrocnemius. 

a.  The  muscle=nerve  preparation. 

r  Appliances. — Frog  board  and  pins;  operating  case; 
glass  nerve-hooks,  like  Fig.  11,  A,  made  as  follows:  Take 
a  10  cm.  piece  of  glass  rod,  heat  and  draw  in  center  to 
about  1^2  mm.  diameter;  cool,  cut  in  two,  heat  the 
points  to  smooth  them  and  bend  the  end  over  to  form 
the  hook. 


Fig.  11. 

Fig    11.  A.  Glass  nerve-hook;   for  description  see  IX=a=/.      B.  Gastro- 
cnemius muscle-nerve  preparation.     For  description,  see  text  IX=a=j. 

Simple     myograph    or    muscle    lever    (See    Fig.    13). 
Watch  glass   with  salt  crystals.    20  cm.  of  thick  coppei 
wire. 
2.    Preparation. — Pith    a   frog    and   fix   to   frog  board,    with 
dorsum    up. 

It  will  be  taken  for  granted  that  the  student  is  familiar 
with  the  anatomy  of  the  frog's  leg  and   thigh.     The  ac- 

56 


GENERAL  PHYSIOLOGY 


57 


companying    cuts    may    serve    to    refresh    the    memory. 

(Fig  12) 
j.   Operation.  —  To  make  a  gastrocnemius  '■'■muscle  nerve  prep 

aration. " 

(1)  Make,  with  scissors,  a  circular  cutaneous  incision 
around  the  tarsus,  corresponding  with  the  lower  end 
of  cut  B.  Make  a  longitudinal  cutaneous  incision, 
beginning  at  the  margin  of  the  circular  incision  where 
it  crosses  the  external  aspect  of  the  tarsus,  carry  it 
along  the  tibia,  along  the  course  of  the  biceps  femo 
ris  muscle,  over  the  pyriformis  to  the  posterior  end 


Fig.  12. 
Fig.  12.     Showing  the  muscles  of  the  frog's  thigh  and  leg. 


of  the  urostyle,  along  the  whole  extent  of  the  uros- 
tyle.  From  the  posterior  end  of  the  urostyle  make 
an  incision  posteriorly  and  ventrally,  for  1  or  2  cm. 
Grasp  the  free  margin  of  the  skin  at  the  point  of 
the  circular  incision  and  with  a  quick  traction 
toward  the  head  of  the  frog  the  skin  will  be  re- 
moved from  the  whole  field  of  operation. 
(2)  Pass  a  point  of  the  fine  scissors  under  the  glisten- 
ing tendon  of  the  biceps  femoris  where  it  is  inserted 


58  LABORATORY  GUIDE  JN  PHYSIOLOGY. 

into  the  tibia,  taking  care  not  to  injure  any  of  the 
neighboring  tissues.  Sever  the  tendon.  Grasp  its 
free  end,  lift  the  biceps  up,  carefully  cutting  the 
delicate  connective  tissue  which  joins  it  to  neigh- 
boring structures;  sever  its  heads.  The  removal  of 
the  biceps  and  a  separation  of  the  cleft  which  the 
biceps  occupied  reveals  three  blood  vessels  and  the 
large  trunk  of  the  sciatic  nerve.  Which  of  the  blood 
vessels  is  the  sciatic  artery?  Which  the  sciatic 
vein?     Which  the  femoral  vein? 

Grasp  and  lift  up  the  posterior  end  of  the  urostyle, 
sever  the  ilio-coccygeal  muscles,  remove  the  urostyle. 

The  sciatic  plexuses  formed  by  the  *7th,  8th  and 
9th  pairs  of  spinal  nerves  will  be  revealed. 

(4)  Pass  a  glass  nerve  hook  under  the  sciatic  nerve, 
gently  lift  it  up,  severing,  with  the  scissors,  the  con- 
nective tissue.  The  pyriformis  muscle  must  also 
be  divided.  The  whole  length  of  the  sciatic  nerve 
may  thus  be  readily  dissected  out.  Care  should  be 
taken  not  to  stretch,  pinch  or  cut  the  nerve  during 
this  process.  Lay  the  nerve  upon  the  gastrocne- 
mius muscle. 

(5)  Grasp  the  triceps  femoris  muscle,  pass  a  blade  of 
the  scissors  under  its  tendon;  sever,  and  remove 
the  whole  mass  of  muscles  anterior  to  the  femur. 
In  a  similar  manner  remove  the  muscles  posterior 
to  the  femur. 

(6)  Grasp  the  tendo  achillis,  sever  low  down  at  X; 
lift  up  the  gastrocnemius,  sever  the  tibia  and  its 
associated  muscles  as  near  to  the  knee  joint  as 
possible. 

(V)  Sever  the  femur  at  the  juncture  of  its  middle  and 
upper  thirds.  The  finished  preparation  has  the 
characteristics  shown  in  Fig.  11 — B.  A  segment  of 
the  vertebral  column  may  or  may  not  be  left  on. 


GENERAL  PH YSIOLOG V. 


59 


b.  The  indirect  stimulation  of  the  gastrocnemius. 

4.  Observations. —  To  mount  the  muscle-nerve  preparation  in 
the  myograph.  Fix  the  femur  in  the  clamp  (Fig.  13-c); 
place  a  piece  of  filter  paper,  wet  with  normal  saline  solu- 
tion, upon  the  glass  nerve  support  (s);  lay  the  nerve  upon 
the  support;  make  a  longitudinal  slit  in  the  tendo 
achillis,  pass  the  hook  of  the  muscle  lever  through  the 
slit  and  so  adjust  the  height  of  the  clamp  as  to  bring  the 
lever  into  a  horizontal  position. 


Fig.  13. 

Fig.  13.     Simple  myograph,   with  a   femur-clamp  (<-),   and  a  glass 
plate  (s)  for  a  nerve  rest. 

a.  Mechanical  Stimulation. — (1)  Snip  off  with  scissors  the 
central  end  of  the  sciatic  nerve.  If  the  muscle  in- 
stantly contracts,  thereby  lifting  the  lever,  the  ob- 
server will  know  that  his  preparation  is  successful. 
If  it  does  not  respond  to  the  first  stimulation  it  may 
to  a   second  or  subsequent  one.      If   it   responds  to 


60  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

later  stimuli  but  not  to  the  first  ones,  one  may  con- 
clude that  in  making  the  preparation  a  portion  of 
the  central  end  of  the  nerve  was  killed. 

(2)  What  may  one  conclude  if  the  muscle  responds 
to  stimuli  applied  to  the  central  end  of  the  sciatic 
nerve,  but  later  fails  to  respond  to  stimuli  applied 
farther  along  the  course  ot  the  nerve,  i.  e., nearer  the 
muscle? 

/>.    The i  mal  Stimulation. 

(3)  Make  and  mount  a  fresh  preparation.  Heat  the 
copper  wire  in  a  gas  flame  and  touch  the  end  of  the 
nerve  with  the  hot  wire.  If  the  preparation  has 
been  successful  the  muscle  will  respond  by  a  contrac- 
tion. If  the  preparation  is  a  good  one  save  at  least 
2/l  of  the  nerve  for  the  subsequent  experiment. 

c.    Chemical  Stimulation. 

(4)  Cut  off  the  part  of  the  nerve  which  is  dead  and 
lay  the  central  end  of  the  still  functional  nerve  in  a 
saturated  solution  of  common  salt.  Await  results. 
Record  all  results. 


X.     Variation    in    the   method   of  applying   mechanical, 
thermal    and    chemical    stimuli. 

/.   Appliances. — Operating     case;    kymograph;    myograph; 

3  frogs. 
2.  Preparation.  —  Much  interest  will  be  added  to  these 
experiments  if  a  permanent  record  be  made  of  the  move- 
ments of  the  lever  when  the  muscle  responds  to  a  stim- 
ulus. The  most  practical  method  of  recording  these 
movements  is  to  cause  the  lever  point  to  trace  them  upon 
a  moving  surface.  It  is  customary  to  use  a  rotating  cyl- 
inder, upon  which  is  fixed  a  glazed  paper  which  may  be 
smoked  in  a  gas  flame.  The  kymograph — wave  writer — 
an  instrument  much  used  for  this  purpose,  consists  of  a 
metallic  cylinder  and  a  clock  work  for  its  propulsion 
(See  Fig.  14.) 

Describe    the    structure  of  the  kymograph  giving  fig- 
ures. 

To  prepare  the    kymograph  for  work.       (See  Appendix 
A-6.) 

To  curarize  a  frog.  (See  Appendix  A-5.) 
j.  Operation.  —  To  make  a  sartorius  preparation.  After  the 
frog  has  come  under  the  influence  of  the  curare,  pass  a 
blade  of  the  fine  scissors  under  the  tendon  of  insertion 
of  the  sartorius;  cut  it  as  close  to  the  tibia  as  possible; 
grasp  the  tendon  with  forceps  and  carefully  lift  it  up, 
cutting,  with  the  scissors,  the  connective  tissue  which 
holds  the  muscle  in  place;  follow  it  as  far  as  possible  and 
get  as  much  of  the  tendon  of  origin  as  possible.  Mount 
this  preparation  by  tying  a  thread  to  each  terminal  tendon, 
and    fixing    one    thread  to  the  myograph  clamp  and  the 

61 


62 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


other  to  the   tracing  lever.     This  muscle  should  not  be 
made  to  lift  as  heavy  a  weight  as  is  used  for  the  gastroc 
nemius. 
Observations, 
{a)   Direct  versus  indirect  stimulation. 

(1)  Put  saturated  salt  solution  upon  the  sartorius — di- 
rect stimulation.  If  it  responds  take  a  tracing  of  the 
response. 


Fig.  14. 
Fig.  14.     The  Kymograph.      For  description  see  Appendix  C. 

(2)  Mount  the  second  sartorius  and  try  mechanical 
and  thermal  stimuli,  tracing  and  recording  results. 

(3)  Prepare  and  mount  a  gastrocnemius  preparation, 
from  a  frog  that  was  not  curarized.  Apply  various 
stimuli  to  the  nerve — indirect  stimulation — as  in  the 
previous  lesson  and  record  results. 


GENERAL  PHYSIOLOGY.  63 

(b  )    Qualitative  variation  of  stimuli. — Make  and  mount  a 
gastrocnemius   preparation  for  indirect  stimulation. 

(5)  Study  the  response  to  the  following  variations  of 
mechanical  stimuli  :  cutting,  pinching,  tapping, 
pricking. 

(6)  Study  the  responses  to  the  following  variation  of 
thermal  stimuli  :  ice,  hot  wire. 

(V)  How  does  the  muscle  respond  to  indirect  stimula- 
tion with  glycerine,  alcohol  ? 
(V)    Quantitative    variation    of    stimuli.       Use    gastroc- 
nemius preparation. 

(8)  Mechanical  stimuli  :  light  tapping,  heavy  tapping. 

(9)  Thermal  stimuli :  Touch  the  nerve  with  the  wire 
which  has  been  held  in  boiling  water,  i.e.,  100°  C. 

Touch    the    nerve  with    a  wire  which    has    been 
heated  to  redness  in  a  gas  flame. 

(10)  Chemical  stimuli :  Put  the  end  of  the  nerve  into 
0.6  %  solution  of  common  salt.  Follow  this  with  y2 
saturated  solution  of  common  salt.  Compare  the 
results  with  those  obtained  when  a  saturated  solu- 
tion was  used. 

(a7)    Variation   in  the  length  of  time  of  applying  stimulus. 
Use  gastrocnemius  preparation. 

(11)  Cut  off,  or  pinch  off  the  nerve  very  slowly.  This 
may  be  done  so  slowly  and  with  such  a  gradual  in- 
crease of  pressure  as  to  cause  no  contraction  of  the 
muscle. 

(12)  Put  the  central  end  of  the  sciatic  into  tepid 
0.6  °/0  NaCl  solution,  and  gradually  bring  to  a 
boil,  protecting  the  muscle  and  that  part  of  nerve 
not  in  the  solution,  with  absorbent  cotton  moistened 
in  normal  saline  solution. 

The  nerve  may  be  functionally  destroyed  without 
causing  a  contraction  of  the  muscle. 


64  LABORATORY  GUIDE  IN  PHYSIOLOGY 

(13)  Put  the  central  end  of  the  nerve  into  Na  CI  0.6  % 
and  gradually  add  salt  to  saturation.  Take  another 
preparation,  put  the  nerve  into  a  few  drops  of 
NaCl  0.6  °J0.  Add  alcohol  drop  by  drop  until  the 
mixture  is  about  90  %  alcohol.     Record  results. 


XI.     Electricity  as  a   stimulus.     The   galvanic  current. 

/.  Appliances. — Operating  case;  3,  10  cm.  pieces  of  uncov- 
ered copper  wire;  a  piece  of  zinc;  beaker;  a  Daniell 
cell;  kymograph;  myograph;  simple  contact  key;  4  cov- 
ered battery  wires;   2  frogs. 

2.    Preparation. 

(1)  Curarize  a  frog. 

(2)  To  prepare  a  u  water  element,"  take  a  small  bright 
piece  of  zinc,  wind  one  end  of  a  10  cm.  piece  of  cop- 
per wire  around  it,  remove  the  glass  plate  from  the 
middle  clamp  of  the  myograph,  clamp  tvc  copper 
wires  so  that  one  or  two  centimeters  of  wire  will  ex- 
tend out  horizontally  on  one  side  of  the  clamp,  while 
the  other  longer  ends  extend  out  on  the  other  side; 
one  of  these  is  wound  around  the  piece  of  zinc.  Bend 
these  long  ends  down  to  the  perpendicular.  Do  not 
allow  these  wires  to  touch  each  other  in  any  part  of 
their  course. 

(3)  Charge  the  Daniell  cell  (See  Appendix  A-4),  insur- 
ing the  proper  amalgamation  of  the  zinc.  Do  not  put 
the  zinc  into  the  cup  until  the  cell  is  to  be  used. 

J.   Experiments  and  Observations. 

(1)  Take  two  coins  of  different  metals,  preferring  cop- 
per and  silver.  With  a  knife  or  file  brighten  on  the 
circumference  of  each  two  small  surfaces  removed 
from  each  other  by  \  to  \  the  circumference.  Touch 
each  coin  separately  to  the  tongue.  Now  bring  the 
two  coins  into  close  contact  at  bright  points,  leaving 
the  other  two  fresh  surfaces  in  such  a  position  that 
the  tongue  may  touch  both  at  the  same  time.     Touch 

65 


66  LABORATORY  GUIDE  IN  PHYSIOLOGY, 

the  coins  with  the  tongue  as  indicated.  Is  there  any 
difference  in  the  sensation  which  the  tongue  receives 
in  these  two  experiments  ?  Record  results,  account- 
ing for  phenomena. 

(2)  While  in  the  operation  of  making  a  gastrocnemius 
preparation,  after  the  sciatic  nerve  has  been  freed  from 
the  other  structures  in  the  thigh,  slip  the  glass  nerve- 
hook  under  it  so  that  the  handle  of  the  nerve-hook 
will  hold  the  nerve  away  from  the  other  tissues.  Press 
the  end  of  a  copper  wire  against  the  muscles  of  the 
thigh,  touch  the  silver  probe  to  the  sciatic  nerve,  then 
to  the  copper  wire,  first  separatel)7,  then  simultane- 
ously. 

Vary  the  experiment  by  using  other  combinations: 
Silver  and  steel,  copper  and  steel,  etc.  Note  briefly  the 
original  observations  of  Galvini.  Are  the  observations 
just  made  different  in  any  essential  respect  from  the 
observation  which  led  to  the  discovery  of  what  we  call 
galvanic  electricity  ? 

(3)  Complete  the  gastrocnemius  preparation,  mount  the 
muscle  in  the  myograph,  place  the  nerve  across  the 
horizontal  ends   of    the  two  wires,   lift   the  beaker  of 
water  and  immerse  the  two  pendant  plates — the  cop 
per  wire  and  the  piece  of  zinc. 

If  the  experiment  is  successful  the  muscle  responds 
vigorously.  Is  there  any  chemical  action  in  this  water 
element?  If  so,  describe  it.  Would  oxidized  or  tar- 
nished plates  answer  as  well  as  bright  ones? 

(4)  Mount  another  gastrocnemius  preparation,  adjust 
the  Daniell  cell  for  action,  set  up  the  electric  apparatus 
as  shown  in  Plate  II,  Fig.  5,  clamp  the  two  exposed 
poles  (p.)  in  the  middle  clamp  so  that  the  ends  are 
exposed  for  about  two  centimeters.  Place  the  nerve 
across  the  poles.  Adjust  the  kymograph  for  tracing 
a  myogram. 


GENERAL  PHYSIOLOGY.  67 

(a)  Close  the  key,  i.  e.  "make"  the  current,  and  hold 
the  key  down  for  several  seconds.  Note  results 
and  take  tracing. 

(/>. )  Open   the  key,  i.  e.  "Break  the  current." 
Note  results  and  take  tracing. 

(7.)  Make  and  break  the  current  during  one  rotation 
of  the  drum.  If  there  is  a  response  on  both  make 
and  break,  so  time  the  closing  and  opening  of  the 
key  that  these  will  come  in  pairs  with  a  consider- 
able pause  between.  Before  fixing  the  tracing, 
(see  Appendix  A-7.)  mark  each  wave  which  was 
the  effect  of  making  the  current  m.,  and  each  wave 
which  was  caused  by  breaking  the  current,  b. 

(5)  Prepare  and  mount  a  sartorius  from  the  curarized 
frog.  Bring  the  two  poles  into  contact  with  the 
muscle,  and    repeat  the  experiments  suggested  under 

(6)  In  experiments  (4)  and  (5)  the  observer  has  applied 
electric  stimulation  of  medium  strength  both  directly 
and  indirectly  to  the  sartorius  and  gastrocnemius 
muscles.  He  is  justified  in  formulating  certain  con- 
clusions— subject  to  subsequent    modification. 

Formulate  conclusions. 

(7)  Describe    minutely  the  chemical    and  physical  proc 
esses  going  on  in  the  active  Daniell  cell. 


XII.     Stimulation     with     the     constant     current.     The 
simple  rheocord. 

/.  Appliances. — Operating  case,  kymograph  and  myograph; 
3  or  4  Daniell  cells;  simple  rheocord;  materials  for  mak 
ing  nonpolarizable  electrodes,  (see  demonstration 
VIIT);  PohPs  commutator  with  cross-bars;  Du  Bois 
Reymond  key;   9  wires;   8  frogs. 

2.  Preparation. 

(].)   Make  a  pair  of  N  P  electrodes. 

(2.)  Set  up  apparatus  as  shown  in  PI.  II,  Fig.  6. 

J.    Operation. — Make  and   mount   a    gastrocnemius   prep.i 
ration  and  so  adjust  the  nerve  to  the  electrodes  that  the 
current   will    be    a  "descending"    one,   i.   e.    so  that  the 
kathode  will  be  nearer  to  the  muscle  than  is  the  anode 

4.   Observations. 

(1)  (a)  Open  the  short-circuiting  Du  Bois-Reymond 
key — i.  e.  make  the  long  circuit. 

(b)  Close  the  key,  thus  breaking  the  long  circuit,  or 
muscle  circuit. 

(c)  Take  a  tracing  of  a  series  of  alternating  make  and 
break  shocks  with  descending  current. 

(d)  Take  a  tracing  with  ascending  current.  How  may 
one  change  the  direction  of  the  current  along  the 
nerve  without  changing  the  adjustment  of  nerve 
and  electrodes  ? 

(2)  (a)  Give  the  preparation  a  stronger  stimulus  by 
joining  two  cells.  Should  one  join  the  cells  in  series 
or  multiple  arc  ?     Why  ? 

(b)  Take  a  tracing  as  before  using  the  descending 
current. 


GENERAL  PHYSIOLOGY. 


69 


(c)  Vary  the  experiment  by  the  use  of  the  ascending 
current. 

(3)  (a)  Increase  further  the  strength  of  the  stimulus  by 
the  use  of  a  battery  of  three  or  four  cells. 

Record  effect  of  descending  current, 
(b)  Record  effect  of  ascending  current. 

(4)  Set  up  electrical  apparatus  with  simple  rheocord  as 
shown  in  PI.  II.  Fig.  V.  Instead  of  making  a  tracing 
tabulate  the  results. 

(a)  Adjust  for  stimulation  with  the  minimum  descend- 
ing current.  Make  the  muscle  circuit  and  record 
whether  the  muscle  contracted,  or  remained  at  rest. 

(b)  Stimulate  with  minimum  ascending  current  and 
record. 

(c)  Gradually  strengthen  the  current,  recording  at 
each  position  of  the  slider  the  results  for  both  de- 
scending and  ascending  currents,  make  and  break. 

The  folio wiiii*  form  of  table  should  be  used: 


STRENGTH 

OF 
CURRENT. 


DESCENDING. 

Make      I    Break. 


ASCENDING. 

Make.     I    Break. 


Weak. 

Medium. 

Strong 


Contract.:     Rest. 


(5)  Sum  up   the  day's  work  in  a  series  of  conclusions. 


XIII.     The  effect  of  the  induced  current. 

/.  Appliances. — Operating  case;  inductorium  with  Neef 
hammer;  contact  key;  DuBois  Reymond  key;  7  wires; 
1  Daniell  cell;  materials  for  making  hand  electrodes  [2 
No.  24  or  28  wires  ^4  meter  long,  2  pieces  of  capillary 
rubber  tubing  4  or  5  cm.  long,  thread];  2  frogs. 
2.  Preparation. — (a)  To  ?nake  hand  electrodes  for  use  with 
induced  currents.  Push  a  thin  wire  through  a  piece  of 
capillary  rubber  tubing  (capillary  glass  tubing  may  be 
used  instead  of  the  rubber),  bring  two  such  side  by  side 
and  wrap  thread  around  them.  If  glass  tubing  be  used 
the  wire  will  need  to  be  fixed  in  the  tubes  with  a  drop  of 
sealing  wax. 

Such  a  pair  of  hand  electrodes  are  shown  in  Figure  9> 
page  52. 

(b~)  Set    up    electric    apparatus    with    contact    key  in 
primary  circuit  and   short-circuiting  key  in  secondary 
circuit. 
j.    Operation.  —  Make  and  mount  gastrocnemius  prepara- 
tion. 
4.    Observations. 

(1)  Take  tracings  of  the  contractions  produced  by  a 
series  of  "  make,  induction  shocks  "  applied  indirectly. 
The  "  make,  induction  shock"  is  obtained  as  follows: 
(a)  With  primary  circuit  not  interrupted  by  the 
Neef  hammer,  but  closed  and  opened  only  by  the 
contact  key;  open  the  short-circuiting  key  of  the  in- 
duced circuit. 

(h)  Close  the   contact  key  of   the   primary  circuit,  a 
make    induction  shock — i.    e.,  a   shock    in    the  in- 
70 


GENERAL  PHYSIOLOGY.  71 

duced  circuit  caused  by   a  closure  of   the  battery- 
circuit — will  stimulate  the  preparation. 

(c)  Close  the  short-circuiting  key  in  the  secondary 
circuit. 

(d)  Open  or  break  the  primary  circuit.  An  induced 
break  shock  occurs  in  the  secondary  circuit  but  it 
is  short-circuited  by  the  closed  Du  Bois  Reymond 
key.  If  while  the  drum  rotates  one  makes,  in 
close  succession,  the  changes  above  indicated — 
a-b-c-d-a-b-c-d  etc. —  there  will  be  produced  a 
series  of  contractions,  all  the  result  of  stimulation 
by  ?nake  induction  shocks. 

(2)  Take  a  tracing  of  the  contractions  resulting  from 
a  series  of  indirectly  applied  break  induction   shocks. 

(3)  By  leaving  the  short-circuiting  key  open,  one  may 
get  a  series  of  contractions  due  to  alternating  make 
and  break  induction  shocks.  Let  these  be  re- 
corded in  pairs  upon  the  kymograph. 

(4)  Determine  the  distance  which  the  secondary  coil 
may  be  removed  from  the  primary  coil  and  get  any 
response  to  the  make  or  break.  Which  is  more 
effective  make  or  break  ?  Can  one  find  a  position 
of  the  secondary  coil  where  there  are  only  make  or 
break  shocks?  What  are  the  limits  of  this  position  ? 
Within  the  limits  of  that  position  where  both  make 
and  break  contractions  occur  are  there  differences 
in  the  height  of  the  make  or  break  waves?  Is  there 
a  position  of  maximum  height  for  both  waves?  If 
not,  is  there  a  position  of  maximum  height  for  each 
wave  ? 

Make  a  tracing  on  a  slowly  rotating  drum,  while 
gradually  moving  the  secondary  coil  from  the  great- 
est distance  which  gives  a  contraction  up  to  the 
zero  point.      Record   at  intervals  upon   the  tracing 


72  LABORATORY  GUIDE  IN  PHYS/OLOGY. 

the  positions  of  the  secondary  coil  at  that  point  in 
the  tracing. 

(5)  Still  leaving  the  short-circuiting  key  open  make 
and  break  the  primary  current  as  rapidly  as  it  is  pos- 
sible to  close  and  open  the  key  in  the  primary  circuit. 
Take  tracing. 

(6)  So  adjust  the  apparatus  that  the  Neef  hammer  is 
brought  into  the  primary  circuit,  thereby  making 
and  breaking  that  circuit  with  each  vibration  of  the 
hammer.  Mount  a  fresh  gastrocnemius,  adjust  the 
kymograph  for  slow  or  medium  rotation. 

Close  the  short  circuiting  key;  close  the  key  in 
the  primary  circuit.  The  Neef  hammer  should  start 
to  vibrating  and  continue  to  do  so  as  long  as  the 
primary  circuit  is  closed.  Start  the  kymograph. 
After  an  abscissa  a  few  centimeters  in  length  has 
been  traced  upon  the  drum,  open  the  short-cir- 
cuiting key.  If  the  experiment  is  successful  the 
muscle  will  be  tetanized.  Allow  the  tetanizing  cur- 
rent to  operate  until  a  tetanus  tracing  several  centi- 
meters in  length  has  been  traced.  Close  the  short- 
circuiting  key. 

After  a  few  moments  the  muscle  may  be  again 
tetanized,  and  repeatedly  so  until  exhausted. 


XIV.    The  work  done  by  a  muscle,    a.  To  determine  the 

amount  of   work  done  by    a  single  contraction. 

b.  To  determine  the  total  amount  of  work 

done  by  a  muscle,      c.   Reaction 

changes  in  fatigued  muscle. 

/.  Appliances. — Same  as  in  lesson  XIII.;  also  50  gramme 
weight  and  20  or  30  gramme  weight. 

2.  Preparation. — Arrange  electrical  apparatus  for  a  series 
of  break  induction  shocks. 

,'.  Operation.  —  Make  and  mount  a  gastrocnemius  prepara- 
tion for  indirect  stimulation. 

^.  Observations. — Upon  a  slow  drum  record  in  close  order  a 
series  of  break  contractions. 

a.  To  determine  the  amount  of  work  done  by  a  single 

contraction. 

(I)    What  weight  is  lifted? 

(2  )   How  high  is  it  raised  ? 

(3)  What  is  the  ratio  between  the  height  of  the  curve 
traced  by  the  lever  and  the  height  through  which 
the  weight  was  raised? 

(4)  Let  W  =  work  done. 

g  =  weight  lifted. 

h  =  height  of  curve  traced  by  lever. 
/inconstant  of    the  apparatus,   in    this     case 
the   ratio   between  the   lever  arms.     Then 
W=*.  g.  h. 
r5)   Express  the  amount  of  work  in  ergs. 

b.  To  determine  total  work  done. 

(5  )  How  many  times  was  the  weight  lifted  before  the 
muscle  was  fatigued? 

73 


74  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(6)  Through  what  average  height  was  the  weight 
lifted? 

(7)  Has  the  value  of  k  or  g  changed? 

(8)  Give  a  formula  for  total  height  (H=). 

(9)  Give  a  formula  for  total  work  done  (W  =  ). 

(10)  Express  in  ergs,  the  total  work  done  by  the  muscle. 

(11)  In  the  fatigue  tracing  did  the  lever  continue 
throughout  the  observation  to  fall  back  to  the  orig- 
inalabscissa  ?  If  not,  describe  any  general  changes 
in  the  abscissa. 

c.  Reaction  changes. 

(12)  Apply  a  piece  of  neutral  litmus  paper  toj  the 
fresh  muscle  tissue  of  the  frog  from  which  your 
specimen  was  taken.     Record  result. 

(13)  Apply  a  piece  of  litmus  paper  to  a  fresh  cut  sur- 
face of  the  fatigued  muscle.     Record  results. 

(14)  What  is  the  reaction  of  the  muscle  of  a  frog 
after  rigor  mortis  has  been  established? 

(15)  What  is  the  reaction  of  fresh  urine? 


XV.    Demonstration:   Electrotonus;  to  determine  the  effect 
of  a  constant  current  upon  the  irritability  of  a  nerve. 

At  the  beginning  of  this  century  Ritter  discovered  that 
the  vital  properties  of  irritable  and  contractile  tissues 
were  modified  when  subjected  to  a  constant  battery  cur- 
rent. This  modified  condition  was  called  galvantsmus. 
During  the  first  half  of  this  century  the  subject  was  in- 
vestigated by  Nobili,  Mattencci,  Valentin  and  Du  Bois- 
Reymond  ;  the  last  named  substituted  the  word  electro- 
tonus iox  galvanismus  and  further  modified  the  terminology. 
It  remained  for  Pfliiger  (Untersuchungen  iiber  die  Physio- 
logic des  Electrotonus,  Berlin,  1850)  to  rework  the  whole 
field,  to  correct,  to  elaborate,  and  finally  to  formulate  laws. 
a.    Preliminary  experiment. 

1.  Appliances. — Muscle- signal ;  2  Du  Bois-Reymond  keys; 
2  Daniell  cells  ;  commutator  ;  S  wires  ;  salt. 

2.  Preparation. — Set   up  electrical  apparatus  as   shown  in 
PI.  II.  Fig.  8. 

J.    Operation. — Make    and     mount   in   the    muscle  signal    a 

gastrocnemius  preparation. 
4.      Observations. 

(1)  In  which  position  must  the  bridge  of  the  commuta- 
tor stand  to  give  a  descending  current?  Mark  that 
side  of  the  commutator  D.      Mark  the  opposite  side  A. 

(2)  With  a  descending  current,  which  pole  is  the 
kathode,  a  or  b  ? 

(3)  PI.  II.  Fig.  8-p  represents  the  glass  plate  of  the 
muscle  signal.  So  arrange  the  triangular  platinum 
electrodes  that  there  shall  be  a  distance  of  about  1 
cm.  between  the  electrodes,  and  both  electrodes  near 

75 


76  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

that  end  of  the  plate  farthest  from  the  muscle.  Lay 
the  nerve  over  the  electrodes  and  along  the  glass 
plate.  The  segment  of  nerve  which  lies  upon  the 
glass  plate  between  the  electrodes  and  the  muscle 
may  be  subjected  to  various  stimuli,  mechanical  and 
chemical.  Sterling  (Prac.  Phys.,  p.  244)  uses  salt. 
At  a  point  about  1  cm.  from  the  electrodes,  marked  x 
in  the  figure,  place  upon  the  nerve  trunk  as  many  fine 
crystals  of  common  salt  as  would  be  taken  up  on  the 
point  of  a  penknife.  Moisten  these  salt  crystals  with 
a  drop  of  water.  While  the  salt  solution  is  per- 
meating the  sheath  of  the  nerve  trunk,  adjust  the  com- 
mutator for  a  descending  current.  When  the  muscle 
begins  to  twitch,  note  the  effect  upon  the  signal.  The 
contractions  become  more  and  more  tetanic  in 
character. 

(4)  Close  the  commutator  circuit,  open  the  short-cir- 
cuiting key,  i.  e.,  make  the  "polarizing"  current.  If 
the  experiment  is  successful  the  tetanus  is  more 
marked.     Which  pole  is  nearer  the  point  stimulated? 

(5)  Close  the  short  circuiting  key,  i.  e.,  break  the 
"polarizing"  current.  Reverse  the  commutator; 
make  the  current.  The  muscle  is  put  completely  or 
almost  completely  at  rest.  Which  pole  is  nearer  the 
stimulus? 

(6)  Repeat  (4)  and  (5)  several  times.  It  is  evident 
that  the  irritability  of  the  nerve  to  the  salt  stimulus  is 
increased  in  the  region  of  the  kathode,  and  decreased 
in  the  region  of  the  anode  pole.  This  changed  con- 
dition of  the  nerve  due  to  the  passage  of  a  constant 
current  is  called  electrotonus.  The  state  of  increased 
irritability  in  the  region  of  the  kathode  is  called 
katelectrotonus.  The  decreased  irritability  in  the  region 
oi  the  anode  is  called  anelectrotonus. 


GENERAL  PHYSIOLOGY.  77 

b.  Myographic  record  of  anelecirotonus  and  of  katelectrotonus. 
i.  Appliances. — 3  or  -i  Daniell  cells;  3  Du  Bois- 
Reymond  keys;  contact  key;  2  commutators;  induc- 
tcrium;  2  N-P  electrodes;  18  wires;  kymograph; 
myograph  with  moist  chamber;  2  pairs  of  platinum 
wire  electrodes  to  use  with  induction  currrent. 
2.  Preparation. — Arrange  apparatus  according  to  plan 
shown  in  PI.  II.,  Fig.  9.  Note  that  the  cross  bars 
are  absent  from  the  commutator  in  the  induction  cir- 
cuit. This  enables  one  to  stimulate  the  nerve  at  the 
central  end  (c)  or  at  the  segment  between  the  polar- 
izing electrodes  and  the  muscle  (m),  by  simply  revers- 
ing the  bridge  of  the  commutator  (B). 
J.  Operation.—  Make  and  mount  a  gastrocnemius  prepa 
ration  in  moist  chamber  myograph;  adjust  drum  for 
tracing  myogram.  Adjust  electrodes  as  shown  in 
diagram. 

Test  apparatus  and  preparation  by  sending  single 
make  (or  break)  induction  shocks  through  nerve  at  c 
or  at  m.  Let  there  be  a  typical  response  at  both 
places.  The  secondary  coil  should  be  removed  to  a 
distance  that  gives  a  little  more  than  the  minimum 
stimulus  required  to  cause  a  contraction  of  the  muscle. 

To  close  the  constant  current  "polarizes"  the  nerve 
or,  better,  induces  elect r otonus. 

That  segment  of  the  nerve  between  the  anode  and 
kathode  is  called  the  intra- polar  region. 

Those  segments  centrally  and  distally  located  are 
called  extra-polar. 

The   induced  current  is  called  the  stimulating  cm- 
rent. 
4    Observations . 

(1)  Adjust  for  descending,  polarizing  current.     Stimulate 
at  c,  i.  e.  in  the    region  of  anode.      Note — trace — ex- 


78  LAB  OR  A  TOR  Y  G  UIDE  IN  PH  YSIOL  OCY. 

tent  of  muscle  contraction.  Induce  electrotonus, 
stimulate  again  in  region  of  anode.  If  the  experiment 
is  successful  the  contraction  will  be  found  to  be  de- 
creased or  absent. 

The  nerve  is,  at  the  point  c,  in  a  condition  or  anelec- 
trotonus  [descending  extra  polar  anelectrotonus]. 

(2)  Stimulate  at  m,  or  in  the  region  of  the  kathode. 
Withdraw  polarizing  current.  After  a  few  minutes 
stimulate  again  at  m.  If  the  experiment  is  successful 
the  wave  is  higher  in  the  former  than  in  the  latter 
case. 

The  stimulation  was  made  in  the  region  of  the 
kathode  and  the  nerve  in  a  condition  of  kathelectrototius. 
[Descending  extrapolar  kathelectrotonus] 

(3)  Adjust  for  ascending,  polarizing  current. 
Stimulate  at  m,  i.  e.,  in  the  region  of  the  anode.    The 

contraction  is  weaker   than   in  the  normal  nerve,  or  it 
may  be  quite  absent.     This  region  is  now  in  a  condi- 
tion of  anelectrotonus.      [Ascending  extrapolar  anelec 
trotonus.] 

(4)  Stimulate  in  the  region  of  the  kathode.  The  re- 
sponse is  probably  weak.  Withdraw  the  polarizing 
current.  Stimulate  again  in  the  region  of  the  kathode. 
The  response  is  normal,  i.  e.,  it  is  greater  than  during 
the  electrotonic  condition. 

But  in  descending  extrapolar  kathelectrotonus  the  re- 
sponse was  greater  than  normal.  In  the  experiment 
just  performed  we  stimulated  in  the  region  of  ascend- 
ing extrapolar  kathelectrotonus.  Note  that  the  polariz- 
ing current  is  relatively  strong. 

(5)  Remove  one  cell  from  the  battery  and  repeat  (4.) 
If  the  response  to  stimulation  is  still  weaker  with  than 
without  the  polarizing  current,  reduce  the  strength  of 
the  polarizing  current  still  farther  by  use  of  the  simple 


GENERAL  FHYSIOLOGY.  79 

rheocord.  Finally  with  a  weak  polarizing  current,  the 
stimulus  in  the  region  of  ascending  extrapolar  kathe- 
lectrotonus  causes  a  stronger  response  than  normal. 

The  response  which  the  muscle  makes  must  be 
accepted  as  a  measure  of  the  excitation  which 
it  receives  from  the  nerve.  But  the  excitation 
delivered  by  the  nerve  depends  upon  two  factors,  its 
irritability  and  its  conductivity.  When  the  nerve  is 
stimulated  in  the  region  of  ascending  extra  or  intra- 
polar  kathelectrotonus,  its  increased  irritability  is  of 
no  avail  if  there  is  interposed  between  that  region 
and  the  muscle  a  region  of  decreased  conductivity. 
With  strong  polarizing  currents  the  region  of  the 
anode  is  not  only  decreased  in  irritability  but  also  in 
conductivity. 
Laws  of  electrotonus. 

I.  The  passage  of  a  constant  current  through  a  nerve  in- 
duces a  condition  of  electrotonus  marked  by  an  increased 
irritability  in  the  region  of  the  kathode  {kathelectrotonus) 
and  a  decreased  irritability  in  the  region  of  the  anode 
(aneleclroionus') . 

II.  During  electrotonus  induced  by  a  strong  current  the  con- 
ductivity  is  decreased  in  the  region  of  the  anode.  Further 
— though  not  derived  from  the  foregoing  experiment — "at 
the  instant  that  the  polarizing  current  is  withdrawn  the 
conducting  power  is  suddenly  restored  in  the  region  <f 
the  anode  and  greatly  lessened  or  lost  in  the  region  of 
the  kathode.''' — Lombard,  in  American  text-book  of 
Physiology. 


XVI.     Demonstration:    Pfluger's  law  of  contraction. 

/.  Appliances. — Du  Bois-Reymond  rheocord,  or  simple 
rheocord;  3  Daniel  cells;  muscle  signal  or  myograph 
with  moist  chamber;  2  Du  Bois-Reymond  keys;,  com- 
mutator; 2  N.  P.  electrodes. 

2.   Preparation — Set  up   the  apparatus    with  three  cells  in 
series,  Du  B.-R.  key   as   closing  key.      Commutator  with 
cross-bars,  Du  B.  R.  rheocord  in  short  circuit,  short-cir 
cuiting  key,  the    two  N  P.  electrodes   clamped  in  cham- 
ber of  myograph. 

5>  Operation. — Make  and  mount  a  gastrocnemius  prepara- 
tion. 

4.    Observations. 

(1)  Stimulate  with  make  and  break  of  the  weakest  pos- 
sible descending  current. 

Record  results  in  such  a  table  as  that  suggested  in 
laboratory  lesson  XII. 

This  table  shows  what  response  (contraction  or 
rest)  the  muscle  gives  on  the  making  and  breaking  of 
the  descending  current  and  on  the  making  and  break- 
ing of  the  ascending  current. 

It  also  shows  in  a  marginal  column  the  gradual  in- 
crease of  the  strength  of  the  current  through  gradual 
increase  of  resistance  in  the  short-circuiting  rheocord. 

(2)  Make  and  break  with  weak  ascending  current.  If 
the  conditions  are  typical  the  muscle  will  contract  on 
making  both  ascending  and  descending  current. 

(3)  Increase  gradually  the  strength  of  the  electrode  cir- 
cuit, recording  results.  After  a  longer  or  shorter 
transitional  period  in  which  the  result  will  be  varied 

80 


GENERA L  Ell )  S/OL OGY. 


81 


by  a  contraction  on  both  the  make  and  break  of  the 
ascending  current,  one  comes  to  a  strength  of  current 
which  causes  a  contraction  on  both  make  and  break 
of  both  descending  and  ascending  current.  This  is 
the  medium  strength  for  the  preparation  and  the  con- 
dition in  question. 

(4)  Let  the  current  be  increased  still  further  and  by 
larger  increments.  After  passing  another  transitional 
stage  one  finally  reaches  a  strength  of  current  which 
causes  a  contraction  on  make  of  descending  current 
and  break  of  ascending  current.  This  is  the  strong 
current  for  the  preparation  under  observation. 

It  not  infrequently  happens  that  through  overstim- 
ulation and  fatigue  of  muscle  the  whole  experiment 
cannot  be  completed  upon  one  preparation  except  by 
increasing  the*  current  by  larger  increments. 

(5)  Pfliiger's  law  of  contraction  may  be  expressed  in  the 
following  table: 


STRENGTH 

OF 
CURRENT. 

DESCENDING. 

ASCENDING. 

Make. 

Break. 

Make. 

Break. 

Weak. 

C 

R 

C 

R 

Medium. 

C 

C 

C 

C 

Strong. 

c 

R 

R 

C 

(6)   But  how  shall  we  account  for  these  results? 

Let  us  recall  some  of  the  laws  which  have  been  dem- 
onstrated. 
Law  I.  The  influence  of  make  and  break  stimulation. 
The  make  contraction  starts  at  the  kathode  and  the  break 
contraction  starts  at  the  anode.  Further,  kathodic  or  make 
contractions  may  be  caused,  by  a  current  which  is  too  weak  to 
cause  anodic  or  break  contractions. 


82  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

Law  II.   A  law  of  Electrotonus. 

The  passage  of  a  constant  current  through  a  nerve  induces  a 
condition  of  electrotomis,  marked  by  an  increased  irritability 
in  the  region  of  the  kathode,  and  a  decreased  irritability  in 
the  region  of  the  anode. 

Law  III.   A  law  of  Electrotonus. 

During  electrotonus  induced  by  a  strong  current  the  con- 
ductivity is  decreased  in  the  region  of  the  anode. 

With  the  help  of  these  laws  account   for  all   the  typical 
phenomena  observed  above. 


PART  II. 
SPECIAL  PHYSIOLOGY. 


BE 


C.     CIRCULATION. 


XVII.     The    circulation    and    its    ultimate    cause,     a.  To 

observe  the  capillary  circulation,    b.  To  observe 

the  action  of  the  frog's  heart. 

a.  To  observe  the  capillary  circulation. 

/.  Appliances. — Cork  board  3  cm.  wide  by  20  cm.  long  and 
about  ^  cm.  thick;  cover  glasses,  18  mm.  in  diameter 
and  10  mm.  in  diameter;  normal  salt  solution;  camel's 
hair  brush  ;  pins  ;  compound  microscope;  sealing  wax  ; 
thread  ;  filter  paper  ;  2  per  cent  croton  oil  in  olive  oil. 

2.    Preparation. 

Pith  two  frogs  the  day  before  the  observation  is  to  be 
made.  At  the  beginning  of  the  laboratory  period  when 
the  observation  is  to  be  made  curarize  the  frog  lightly  by 
the  hypodermic  injection  of  one  drop  of  a  1  per  cent 
solution  of  curare.  Make  a  frog-board  by  cutting  a  hole 
1.5  cm.  in  diameter  near  one  corner  of  the  cork  board 
and  fasten  a  large  cover  glass  over  the  hole  with  sealing 
wax. 

J.  Operation. — After  the  frog  becomes  curarized,  pin  it  out 
ventral  surface  downward  in  such  a  way  as  to  bring  one 
of  the  hind  feet  over  the  hole  in  the  board.  Tie  thread, 
not  too  tightly,  to  the  third  and  fourth  digits,  loop  the 
threads  over  pins  and  gently  separate  the  digits  until  the 
web  is  quite  flat  and  closely  approximated  to  the  surface 

85 


J8  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

of  the  fixed  glass  which  covers  the  hole.  Run  a  film  of 
normal  salt  solution  under  the  web  ;  place  a  drop  of  the 
same  liquid  upon  the  upper  surface  of  the  web  ;  place  a 
small  cover  glass  over  it;  fix  the  board  upon  the  micro- 
scope stage  so  as  to  admit  of  illumination  by  transmit- 
ted light ;  illuminate;  focus  under  low  power. 
4.    Observations. 

(1)  Observe  the  movement  of  corpuscles  within  blood 
vessels  of  varying  size  and  irregular  course.  Make  a 
drawing  of  the  field  of  observation  showing  the  rela- 
tive size,  the  course  and  anastomoses  of  the  blood 
vessels. 

(2)  Observe  whether  the  motion  is  equally  rapid  in  all 
vessels  ;  if  not,  observe  whether  the  slower  currents 
are  in  the  larger  or  the  smaller  channels.  Determine 
which  of  the  vessels  are  arterioles,  which  capillaries, 
and  which  venules. 

(3)  Have  you  seen  evidence  of  intermittent  force  acting 
upon  the  corpuscles?  If  so,  desciibe  its  influence. 
Determine  whether  this  intermittent  force  makes 
itself  evident  in  all  of  the  vessels  ;  if  not,  in  which 
class  of  vessels  is  it  present? 

(4)  Do  the  corpuscles  change  shape?  If  so,  under 
what  circumstances? 

(5)  Remove  the  cover  glass,  dry  the  web  with  filter 
paper,  touch  a  point  with  a  pin  that  has  been  dipped 
into  dilute  croton  oil.  Without  replacing  the  cover 
above  the  web  observe  whether  the  presence  of  the 
croton  oil  effects  any  change  in  the  diameter  of  the 
vessels,  or  in  the  rate  of  the  blood  flow.  If  there  is  a 
change  in  both,  has  one  a  causative  relation  to  the 
other? 

(6)  Note  and  describe  minutely  all  changes  which  take 
place  at  and  near  the   place   touched  with  the  croton 


CIRCULATION.  87 

oil.  If  no  marked  change  is  produced  by  the  croton 
oil,  touch  the  point  with  a  needle  which  has  been 
dipped  into  strong  nitric  acid. 
(7)  Observe  with  a  high  power.  Have  you  noted  di- 
apedesis  of  white  or  of  red  corpuscles.  If  so,  describe 
the  process  minutely. 

b.  To  observe  the  action  of  the  frog's  heart. 

/.  Appliances.  —  Dissecting  board;  fine  scissors;  heavy 
scissors;  pins;  forceps;  watch  glass;  camel's  hair  brush; 
normal  salt  solution;  fine  silk  thread;  ice,  in  a  beaker. 

2.  Preparation. — Pith  a  frog,  lay  it  with  its  dorsal  surface 
upon  the  dissecting  boaid;  stretch  out  its  legs  and  pin 
the  feet  to  the  board. 

j.  Operation  — Make  a  median  incision  through  the  skin 
from  the  pelvis  to  the  mandible;  make  transverse  inci- 
sions and  pin  out  the  flaps.  Raise  the  tip  of  the  epi- 
sternum;  insert  a  blade  of  the  fine  scissors  under  it  and 
divide  it  transversely,  about  ^  cm.  anterior  to  the  tip. 
Raise  the  anterior  segment  of  the  sternum  at  the  point 
of  the  transverse  incision;  insert  the  blade  of  the  strong 
scissors  under  it  and  divide  it  longitudinally  in  the 
median  line.  Withdraw  from  the  board  the  pins  which 
fix  the  anterior  extremities,  make  gentle,  lateral  traction 
upon  the  fore  feet  until  the  split  sternum  is  sufficiently 
separated  to  afford  a  convenient  working  distance  and 
to  plainly  expose  the  whole  heart. 

4.     Observations. 

(1)  Note  rate  of  systole. 

(2)  Note  sequence  of  contraction   of  auricles,  ventricle 
and  bulbus. 

(3)  Note  change  in  shape  of  different  parts. 

(4)  Note  change  in  color  and  the  position  of  the  same 
in  the  heart-cycle. 


88  LABOR  A  TOR  Y  G  UIDE  IN  PHYSIOL  OGY. 

(5)  Carefully  excise  the  heart  including  the  sinus  veno- 
sus  and  the  bases  of  the  posterior  and  two  anterior 
venae  cavae,  also  the  bases  of  the  two  aortic  trunks. 
Place  the  excised  heart  in  a  watch  glass.  Observe 
whether  the  pulsation  continues.  If  so,  what  is  your 
conclusion  regarding  the  relation  of  the  heart  move- 
ments to  the  central  nervous  system? 

(6)  If  the  pulsation  continues,  note  whether  the  rate 
of  pulsation  has  been  noticeably  changed  by  the  ex- 
cision. 

(7)  Bathe  the  heart  with  a  few  drops  of  normal  solution. 
Hold  the  watch  glass  in  the  palm  of  the  hand  and  note 
whether  the  rate  changes. 

(8)  Float  the  watch  glass  upon  ice  water  and  note  the 
results. 

(9)  If  the  heart  seems  vigorous  (otherwise  procure  a 
fresh  one),  carefully  sever  the  sinus  venosus  with  the 
fine  scissors.  Does  the  sinus  continue  to  beat  ?  Does 
the  heart  continue  to  beat  ?     Interpretation. 

(10)  If  the  heart  beats,  sever  the  auricle  from  the  ven- 
tricle through  the  auriculo-ventricular  groove.  Note 
results. 

(11)  If  the  auricles  beat,  divide  them.  If  they  con- 
tinue to  beat,  do  they  follow  the  same  rhythm? 

(12)  If  the  ventricle  becomes  quiescent,  stimulate  it 
either  mechanically  or  with  a  single  induction  shock. 
How  does  it  respond  to  a  single  stimulus?  Continue 
to  subdivide  the  heart  until  the  parts  refuse  to  respond 
to  stimuli. 

(13)  Repeat  the  experiment  and  see  if  the  same  results 
are  reached  on  subsequent  trials.  Note  results  and 
give  your  interpretation. 


XVIII.  The  graphic  record  of  the  frog's  heart=beat. 

/.  Appliances. — Frog  board;  a  straw  or  strip  of  bamboo  20 
cm.  long;  a  cork  about  2  cm.  in  diameter  and  height; 
pins;  needles;  sealing  wax;  parchment  paper;  a  kymo- 
graph, stand  and  lamp;  a  chronograph.  (See  Appendix 
A-  15.) 

2.  Preparation. — Use  a  pithed  or  a  curarized  frog.  Make  a 
heart  lever  after  the  model  shown  by  the  demonstrator. 

j.  Operation. — Open  the  abdomen  of  the  frog  as  described 
under  XVII-b  3  and  expose  the  heart.  Open  the  peri- 
cardium, place  some  resistant  object — a  cover  slip  for 
instance — under  the  ventricle.  So  adjust  the  heart 
lever  that  the  cork  foot  of  the  long  arm  of  the  lever  will 
rest  upon  the  juncture  of  the  auricles  and  ventricle.  If 
the  weight  of  the  lever  seems  to  be  too  great  for  the  heart  to 
move  easily,  the  long  arm  may  be  made  relatively  lighter 
by  placing  a  counterpoise  upon  the  short  arm.  If  the 
tracing  point  of  the  long  arm  has  a  sufficient  excursion 
to  make  a  good  tracing,  bring  the  kymograph  to  a  posi- 
tion where  the  point  will  lightly  touch  the  carboned 
surface  of  the  drum.  The  lever  should  be  nearly  tan- 
gent to  the  surface  of  the  drum,  and  so  arranged  that 
the  rotating  surface  of  the  drum  turns  away  from  the 
tracing  point  of  the  lever  rather  than  toward  it. 

4.    Observations. 

(1)  Note  whether  the  curve  is  a  simple  one  or  com- 
posed of  a  major  wave,  with  crests  superimposed 
upon  it. 

(2)  In  either  case  closely  observe  the  phases  of  the 
heart-cycle  and  determine   the  relation   of  each  part 

89 


90  LABORATORY  GUIDE  /AT  PHYSIOLOGY. 

of  the  cycle  with  each  part  of  the  tracing.  If  the 
tracing  has  a  single  crest,  more  delicately  counterpoise 
the  lever  and  more  carefully  adjust  the  narrow  foot  of 
the  lever  to  the  auriculo-ventricular  groove  and  repeat 
the  experiment. 

(3)  Take  tracings  of  the  auricle  alone.  Compare  these 
with  those  of  the  auriculo-ventricular  groove  and  deter- 
mine the  causes  of  the  variation. 

(4)  Without  altering  the  counterpoise  take  a  tracing  of 
the  ventricle  and  compare  it  with  the  two  preceding 
curves  and  account  for  all  the  differences. 

(5)  Try  to  take  a  double  tracing  with  one  lever  foot 
resting  upon  the  auricle  and  the  foot  of  the  second 
lever  resting  upon  the  ventricle.  The  tracing  points 
must  touch  the  drum  in  a  vertical  line.  Are  the 
crests  synchronous?     If  not,  why? 

(6)  If  a  time  tracing  be  added  by  means  of  the  chrono 
graph   one   may  determine  the  time  relations   of   the 
different  phases  of  the    heart  cycle. 


XIX.  The  apex=beat.     The  heart=sounds. 

/.  Appliances. — A  cardiograph  and  a  transmitting  tambour 
(Marey)  or  materials  for  constructing  them.      A  stetho- 
scope; a  stand  and  support;   clamps;  a  kymograph;  two 
tambour  pans  Nos.  1  and  2;  thin  sheets  of  rubber;  thread; 
corks;  sealing    wax;    tambour    holder;   straws;  needles; 
parchment  paper;  chronograph. 
2.  Preparation. — With  the  materials  furnished  by  the  dem- 
onstrator construct  a  cardiograph  and  a  recording   tam- 
bour, [Appendix  A.,  Nos.  8-9.].     Join  the  tube  of  the 
cardiograph  to  the  tube  of  the  recording  tambour  with 
a  rather  thick-walled    rubber    tube    50   centimeters  in 
length.      Fix   the    recording  tambour  with  clamp  and 
support,  and  bring  it  into  adjustment    for  tracing    the 
cardiogram  upon  the  kymograph.   Adjust  chronograph. 
j.   Operation.  -Let  a  student  remove  the  clothing  from  the 
region  of  the   apex  beat  of   the  heart  and  take,  upon  the 
table,  a  recumbent   dorso-sinistral  position.      In  some 
cases,  however,  better  results  are  obtained  if  the  sub- 
ject sits   beside   the   table.     Place   the   button  of  the 
receiving  tambour  upon  that  point  of  the  thorax  most 
affected  by  the   apex  beat  of  the  heart.     The  move- 
ments of  the  chest  wall  will  be  faithfully  transmitted 
and  magnified  by  the  two  tambours. 
$.    Observations. 

(1)  Note  the  exact  point  upon  the  chest  where  the  apex- 
beat  is  most  distinctly  marked.  Is  it  the  same  for 
different  members  of  the  class? 

In  recording    the    location  of  the  apex- beat  use  the 
bony    landmarks  of  the   chest  rather  than  the  nipple. 

91 


92  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

In  what    intercostal  space  is  it  located  ?     How  far  to 
the  left  of  the  median  line  of  the  sternum? 

(2)  Take  several  cardiograms  from  the  same  individual, 
being  careful  so  to  adjust  the  apparatus  as  to  gain  the 
maximum  excursion  of  the  lever.  What  features  have 
all  of  these  tracings  in  common  ?  What  features  seem 
to  be  accidental  and  nonessential?  What  are  the  causes 
of  the  essential  features?  What  are  the  sources  of  the 
nonessential   features? 

(3)  Take  cardiograms  of  several  individuals.  Do  all  of 
them  possess  the  features  which  seemed  essential  in 
the  first  series,  taken  from  one  individual  ?  If  not,  how 
would  you  account  for  the  difference? 

(4)  With  a  stethoscope,  whose  construction  you  have 
carefully  described  in  your  notes,  listen  to  the  heart- 
sounds  while  the  cardiograph  is  tracing  the  record  of 
the  heart-movements.  Note  that  two  sounds  are  audi- 
ble and  that  there  is  a  noticeable  pause  following  the 
shorter,  sharper  sound;  let  us  call  the  sound  which 
succeeds  the  pause  the  first  sound. 

(5)  With  what  part  of  the  cardiogram  does  the  first 
sound  seem  to  correspond?  With  what  part  of  the 
cardiogram  does  the  second  sound  seem  to  correspond? 
Give  reasons  for  this  correspondence. 

(6)  As  far  as  the  data  will  admit,  enumerate  causes  for 
the  first  sound;  for  the  second  sound;  for  the  essen- 
tial features  of  the  cardiogram. 


XX.     The    flow  of    liquids    through    tubes, 
pressure. 


Lateral 


/.  Appliances. — Reservoir  with  short  discharge  nozzle 
whose  lumen  is  6  mm.  in  diameter;  5  pieces  of  glass 
tubing  whose  lumen  is  about  6  mm.  in  diameter  and 
whose  length  is  60  cm. ;  two  lengths  of  glass  tubing 
whose  lumen  is  about  3  mm.  in  diameter  and  whose 
length  is  60  cm  ;  rubber  tubing  for  joining  up  the  ap- 
paratus; 3  T  tubes  of  6  mm.  tubing;  short  tube  with 
capillary  point  from  each  size  of  tubing;  2  one  liter 
flasks;  2  supports;  a  light  pine  stick  about  6  feet  long; 
compressors  (Mohr's). 
2.  Preparation. — A  resourceful  demonstrator  will  have  no 
difficulty  in  contriving  reservoirs.  It  is  sometimes  not 
easy  to  provide  a  large  class  with  suitable  and  conven- 
ient reservoirs.  The  following  form 
has  proven  very  satisfactory:  A  glass 
tube  about  3  cm.  in  diameter  may  be 
readily  furnished  with  a  glass  nozzle  of 
the  required  size  by  any  glass  blower. 
The  nozzle  should  be  about  3  cm.  from 
one  end  of  the  tube.  That  end  may 
be  closed  with  plaster  of  Paris  and 
filled  with  hard  paraffin  to  the  lower 
margin  of  the  nozzle  opening.  This 
reservoir  may  be  held  upright  by  a 
*^~\t\iCm  support.  When  complete  it  presents 
"  the  appearance  indicated  in  the  accom- 
panying figure. 


94  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

j.    Operation.  —  Mark  upon  the  side  of  the  reservoir  a  point 
36  cm.  above   the  center  of  the   nozzle,  also  a  point  64 
cm.  above  the  nozzle.     While  the  reservoir  is  filled  from 
one  flask  the  water  may  be  caught  in  the  other.      As- 
sume some  convenient  unit  of  time,  as  10  or  15  seconds. 
4..  Observations. — (a)   Fill  the  reservoir  to  the  height  of  64 
cm. 
Allow  the  water  to  flow  from  the  nozzle  freely  into  the 
flasks.     Observe  the  force  with  which  the  jet    issues 
from  the  nozzle  when  the  water  begins  to  flow.     Note 
the  difference  when  the  water  in  the  reservoir  reaches 
the  36  cm.  mark;    the   16  cm.   mark.     What  are  your 
conclusions  ? 

(b)  Velocity. — How  does  the  velocity  of  the  discharge 
vary  with  the  varying  height  of  the  column  of  water  ? 
Why  does  it  so  vary?  Does  it  verify  the  law  of 
Torricelli?  The  rate  at  which  a  fluid  is  discharged 
through  an  orifice  [better  a  nozzle]  in  a  reservoir  is 
equal  to  the  velocity  which  would  be  acquired  by  a  body 
falling  freely  through  a  height  equal  to  the  distance  be- 
tween the  orifice  and  the  surface  of  the  fluid. 

Recall  the  law  of  falling  bodies.  How  far  will  a 
body  fall  in  vacuo,  the  first,  second  and  third  seconds 
respectively?  What  is  the  constant  acceleration 
per  second,  due  to  gravitation  ?  What  is  the 
velocity  at  the  end  of  the  first,  second  and  third 
seconds  respectively?  What  is  the  total  distance 
traversed  at  the  end  of  the  first,  second  and  third 
seconds  respectively?  Let  g  equal  the  constant 
acceleration  (approximately  32  ft.  or  981  cm).  Let 
h  equal  the  total  distance  in  centimeters,  v  the 
velocity  and  t  the  time  in  seconds.  Derive  from 
the  facts  the  following  equations: 
(1)  v=gt. 


CIRCULA  T10N.  95 

From  these  equations  derive: 

(3)  v  — y/2gh;    (approximately  =  4  4.3y/h). 
Expressed  as    a  variation  the    constant  may  be  dis- 
carded and  the  variable  would  read  : 

(4)  v  DoNh,  or  V  :  v  ::  yH  :  vh. 

Verify  the  truth  of  this  mathematically  derived  law. 

(r)  Discharge. — The  discharge  of  liquid  flowing 
through  an  orifice  must  equal  the  product  of  the 
area  of  the  orifice  and  the  velocity  with  which  the 
liquid  flows.  Let  D  equal  the  quantity  of  liquid 
discharged  from  the  nozzle  in  a  unit  of  time,  and  r 
equal  the  radius  of  the  lumen  of  the  discharging 
tube  or  orifice.     Derive  the  formulae: 

(5)  D  =  4  4.3-ryh. 

(6)  D  xryh. 

Where  one  has  to  deal  with  two  variables  he  may 
make  one  of  them  constant  and  verify  for  the  other. 
When  r  is  constant: 

(7)  D  xNh,    or    D  :  d  ::  y'H  :  y/h. 
When  the  height  is  constant: 

(8)  D  xr,    or    D  :  d  ::  R2  :  r2 

Verify  by  experiment  formula  (7)  as  follows: 

During  a  unit  of  time  allow  the  water  to  flow  from  the 

6  mm.  nozzle,  meantime  maintaining  a  fixed  level — 

e.  g.,  at  64  cm. — by  pouring  water  into  the  reservoir 

from  a  flask.     Note  the  amount  of  discharge   (D). 

Make  the  observation   also  for   the  36  cm.  height. 

Verify    formula    (8)    by  determining    D    when    the 

height  is  kept   constant   (64  cm.)   and  the  radius  of 

the  discharge  tube  alone  is  varied.    Use,  for  example, 

a  3  mm.  nozzle.     But  there  is  another  variable  not 

considered  above,  namely,  the  resistance. 

(d)    The  relation   of  discharge   to  resistance. — Attach  to 

the   nozzle   one   length  of  6  mm.  tubing.      Note  the 


96  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

discharge  in  the  unit  of  time.  Attach  a  second 
length  of  the  6  mm.  tubing,  taking  care  that  the 
tubing  is  approximately  horizontal.  Note  the  dis- 
charge in  a  unit  of  time.  What  is  your  conclusion? 
Why  does  the  discharge  decrease  when  the  length 
is  increased  ? 

If   R  equals  resistance   and   L   length  of  tubing, 
does  the  following  expression  represent  the  facts: 

(9)  R  doL? 

Is  the  relation  of  discharge  to  resistance  direct  or 
reciprocal  ? 

Verify  the  following  formula: 

(10)  Dooi- 

We    have    already    found    the    formula    D  oor2\/h. 
Verify  the  formula: 

(11)  Dool^ 

(e)  Pressure. — Disjoin  all  tubes  from  the  reservoir. 
Join  a  T-tube  to  the  nozzle  in  this  position  J_j  join 
a  segment  of  large  glass  tubing  to  the  perpendic- 
ular arm  of  the  T-tube  and  support  it  in  an  upright 
position. 

(1)  Fill  the  reservoir  to  the  36  cm.  mark,  allow 
the  water  to  escape  from  the  distal  end  of  the 
T-tube  during  a  unit  of  time,  meantime  main- 
taining the  height  of  the  water  in  the  reservoir. 
Carefully  note  the  height  at  which  the  water 
stands  in  the  upright  tube — the  piezometer. 

(2)  Repeat  with  water  maintained  at  64  cm. 
height  in  the  reservoir. 

(3)  Join  a  length  of  large  tubing  to  the  distal 
end  of  the  T-tube;  repeat  the  experiment  using 
only  the  64  cm.  height. 

(4)  Join  a  T-tube  with  piezometer  No.  2,  to  the 
distal  end  of  the  segment  of  tubing  just  added 


CIRCULATION.  97 

and  repeat  the  experiment.  (Note:  The 
piezometers  may  be  held  in  position  by  using 
the  two  supports  and  the  pine  stick.)  Does 
the  addition  of  the  last  T  tube  make  any  essen- 
tial change  in  the  height  at  which  the  water 
stands  in  piezometer  No.  1?  Does  the  reading 
of  piezometer  No.  2  agree  with  the  reading  of 
piezometer  No.  1  in  experiment  (2). 

(5)  Add  a  second  segment  of  large  tubing.  Re- 
peat the  experiment.  Does  reading  of  pie- 
zometer No.  2  correspond  with  reading  of  pie- 
zometer No.  1  in  experiment  (3)? 

(6)  Add  piezometer  No.  3.  Repeat  the  experi- 
ment. Does  reading  of  piezometer  No.  3  cor- 
respond with  that  of  No.  2  in  experiment  (4) 
and  with  No.  1  in  experiment  (2)?  Does  read- 
ing of  piezometer  No.  2  correspond  with  that 
of  No.  1  in  experiment  (4). 

(7)  Attach  a  large  capillary,  repeat  observations. 

(8)  Attach  a  fine  capillary  and  repeat  observa- 
tions. What  is  the  relation  of  pressure  to 
height  of  column?  Does  pressure  vary  as 
height  or  as  the  square  root  of  height? 

(9)  (a)  What  is  the  relation  of  pressure  to  the 
central  resistance  (Re)?/,  e.,  the  resistance  be- 
tween the  point  of  observation  and  the  reservoir, 

(&)  What  is  the  relation  of  pressure  to  distal  resist- 
ance (Rd)?  i.  e.,  the  resistance  between  the 
point  of  observation  and  the  point  of  discharge. 

(c)  Which  if  either  of  the  following  formulae  repre- 
sents the  facts: 
(II  )   P  ooRc. 

run  PxRd. 


XXI.     a.  The  flow  of    liquids  through  tubes,  under    the 

influence  of  intermittent  pressure. 

b.  The  impulse  wave. 

a.  The  influence  of  intermittent  pressure. 

/.  Appliances. — Two  glass  tubes  of  about  6  mm.  lumen  and 
about  75  mm.  long;  a  thin  elastic  tube  —  thin  walled 
black  rubber — of  about  the  same  lumen  as  the  glass  tube 
and  about  150  cm.  long;  a  double  valved  strong  rubber 
bulb  (about  7.5  cm,  long);  elastic  tubing,  large  size; 
very  thick  walled  rubber  tubing  for  joining  up  the  appa- 
ratus; Y  tube;  two  flasks,  or  water  receptacles;  heavy 
linen  thread;  a  wide  capillary  and  a  fine  capillary  or 
a  piece  of  glass  tubing  10  cm.  long  for  constructing  the 
same;  500  c.  c.  graduated  cylinder. 

2.  Preparation. — Join  the  large  elastic  tube  to  the  entrance 
valve  of  the  bulb.  Couple  the  two  glass  tubes  closely 
and  join  one  end  to  the  exit  valve  of  the  bulb.  Make 
all  joints  as  close  as  possible  and  tie  tightly  with  thread. 
Draw  a  coarse  and  a  fine  capillary  tube  from  the  10  cm. 
piece  of  glass  tubing. 

j.    Operation. — Clasp  the  bulb  in  the  hand  and  make  rhyth 
matical  contractions  at  the  rate  of  about  fifteen  in  ten 
seconds.     The  process  will,  of  course,  pump   the  water 
from  one  flask  into  the  other. 

4.    Observations. 

a.  Intermittent  force  and  inelastic  tubes. 

(1)  Does  the  stream  of  water  which  is  ejected  from 
the  exit  tube  flow  in  a  constant  or  in  an  intermit- 
tent jet? 

98 


CIRCULATION.  99 

(2)  Attach  a  wide  capillary  and  repeat.  What  is  the 
character  of  the  stream? 

(3)  Attach  a  fine  capillar}-  and  repeat.  Note  the 
results. 

/>.     Intermittent  force  and  elastic  tubes. 

(4)  Disjoin  the  glass  tubing  from  the  bulb  and  join 
the  elastic  tube.  Work  the  bulb  as  directed  above, 
and  observe  the  character  of  the  flow. 

(5)  Join  on  the  coarse  capillary  and  repeat,  noting 
the  change. 

(6)  Replace  the  coarse  capillary  with  the  fine  capil- 
lary and  repeat.  Sum  up  the  results  and  formulate 
conclusions. 

c .      Quantitative  tests. 

(7)  How  much  water  will  be  ejected  through  a  fine 
capillary  tube  in  ten  seconds  in  experiment  (3)  ? 

(8)  How  much  through  a  fine  capillary  in  the  same 
time  in  experiment  (6). 

Note:  In  performing  experiments  (7)  and  (8)  great 
care  should  be  used  to  exert  exactly  the  same  force 
upon  the  bulb.  The  same  capillary  should  be  used  in 
the  two  experiments. 

What  is  the  significance  of  these  two  experiments? 

b.  The  impulse  wave.     The  graphic  record. 

/.   Appliances. — Support;    cork  board  (about  8  by  10  cm.); 

small    glass   rod    about    20    cm.    long;    corks;     needles; 

kymograph;    piece   of    sheet  lead  1  cm.    wide  and  5  cm. 

long;  copper  wire  No.    16. 

2.    Preparation. — Make     a     tracing    lever    from    the     glass 

rod   by  drawing     out   one    end  to    a    rather  fine    pomt 

and    drawing    the    other   to   about    one  half  its  original 

diameter   and   bending    it   to    make     an   angle    of     135°. 

Bend  up  1.5  cm.  of  each  end  of  the  sheet  lead  so  that  it 

will  stand   at  right  angles  to  the  middle  •?   centimeters; 


100 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


bore  the  cork  and  pass  the  larger  end  of  the  tracing  lever 
through  it.     Fix  the  cork  board  to  a  ring  of  the  support 
with  copper  wire;  fix  the  sheet  lead  to  one  end  of  upper 
surface  of   the   cork  board  with  copper  wire  and  pass  a 
needle  through  the  limbs  of  the  lead  bearings  and  the 
lever-cork  in  such  a  way  as  to  bring  the  lever  over  the 
middle  of    the    board.     The   completed    apparatus    will 
have  the  relations  indicated  in  the  accompanying  cut. 
Observations. 
(1)      If  the  finger  be  held  upon  this  elastic  tube  while 
the  bulb  is  being  rhythmatically  squeezed,  a  series 
of  impulses  or  pulsations  will  be  fi=1t  by  the  finger 


Fig.  1(5. 


Place  one  finger  upon  the  elastic  tube  near  the 
bulb,  and  another  three  or  four  feet  from  the  bulb. 
Let  the  bulb  be  pumped  with  sudden,  but  infre- 
quent contractions.  May  one  note  a  difference  in 
the  time  of  pulsation  felt  by  the  two  fingers  ?  If  so, 
which  is  felt  first  ?  Why?  What  is  the  cause  of 
the  pulsation  ? 
(2)  To  get  a  tracing  of  this  pulse,  pass  the  rubber 
tube  across  the  cork  board  under  the  tracing  lever 
[See  Fig.  16] ;  adjust  to  kymograph  and  take  trac- 
ing.    Vary  the   character  of  the   bulb   contractions 


CIRCULATION.  101 

as    follows,    taking     one   complete   rotation    of     the 

drum  for  each  variation: 

(a)     Slow  initial  contraction  of   bulb   and  slow  re- 
laxation 

(<£)   Slow  initial   contraction  of   bulb  and  quick  re 
laxation. 

(V)   Quick   initial  contraction  of  bulb  and    slow  re- 
laxation. 

{d)   Quick    initial     contraction   of    bulb    and    quick 
relaxation. 

(>)   Same  as  d  with  slow  rhythm. 

(/)   Same  as  d  with  rapid  rhythm. 
(3)   Make  a  careful  study   of   these  tracings  and  deter- 
mine : 

(a)  The  characteristic  and  essential  features. 

(b)  The  accidental  and  nonessential  features. 
(V)   The  cause  of    the   essential  ? 

{d)  The  cause  of  the  nonessential  features? 


XXII.     The  laws  of  blood  pressure  determined  from 
an  artificial  circulatory  system. 

i.  Appliances. — Two  large  Y  tubes  of  about  6  mm.  lumen; 
four  medium  Y  tubes,  lumen  about  4  mm  ;  eight  small 
Y  tubes,  lumen  about  2  mm.  ;  six  thick  walled  capillary 
tubes,  about  3  mm.  outside  measurement,  and  lumen  not 
to  exceed  1  mm.  These  capillary  tubes  should  be  about 
15    cm.  long.     Two    T-tubes    of    medium     lumen;    two 


Fig.  17. 

medium  sized  glass  tubes  about  lb  cm.  long.  All 
rubber  tubing  should  be  thin  walled  and  very  elastic, 
and  should  be  in  three  sizes,  corresponding  to  the  glass 
tubes.  Two  pieces  of  large  size,  15  cm.  long,  and  two 
pieces  about  half  that  length  ;  four  pieces  of  medium 
size,  about  40  cm.  long  ;  ten  pieces  of  small  size  ;  bulb; 
heavy  linen  thread;  mercury;  large  glass  receptacle  for 
water,  two  medium  sized  rubber  couplings. 

102 


CIRCULA  T10N.  103 

2.  Preparation. — First,  make  two  manometers  whose  dis- 
tal limb  shall  be  40  cm.  long,  and  proximal  limb  30  cm. 
with  a  horizontal  shoulder  5  cm  long.  Second, 
draw  out  the  two  limbs  of  the  medium  Y  tube 
until  they  are  about  the  same  in  size  as  the 
small  tubing  (Fig.  18).  Third,  construct  the 
Fig.  18.  artificial  circulatory  system  according  to  Fig.  17. 
3-  Operation. — First,  supply  the  manometers  with  mercury 
so  that  there  will  be  12  to  15  cm.  in  each  limb  of  the 
arterial  manometer,  and  5  to  10  cm.  in  each  limb  of  the 
venous  manometer.  If  the  class  is  not  familiar  with  the 
use  and  interpretation  of  the  manometer,  the  demonstra- 
tor should  lead  them  to  discover  all  of  its  essential 
features.  Second,  the  whole  system  should  be  filled 
with  water  and  freed  from  air  before  the  observations 
begin.  Third,  care  should  be  taken  that  no  stoppage  in 
the  system  occurs;  otherwise  the  mercury  may  be 
thrown  out  of  the  manometers  and  lost. 
4     Observations. 

a.    The  manometer  (mercurial). 

(1)  Find  the  actual  pressure  when  the  mercury  in 
the  distal  column  stands  6  cm.  higher  than  that  in 
the  proximal  column.  Derive  the  following  for- 
mula: Actual  pressure^  13.6  -  r2(2  m — ^),  when 
r=radius  of  column  of  mercury,  and  ///the  rise  of 
mercury  in  the  distal  limb  of  the  manometer. 

(2)  Find  the  pressure  per  square  cm.  where  the  ob- 
servation is  the  same.  Derive  the  following  formula: 
Pressure  per  unit  area  =  26.2  m. 

(3)  Which  of  these  data  (actual  pressure  or  pressure 
per  unit  area)  would  be  the  more  valuable  to  record  ? 

(4)  After  the  arterial  circulatory  system  has  been 
freed  from  air  and  is  at  rest,  do  the  proximal  and 
distal  columns  of  mercury  stand  at   the  same  level? 


104  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

If   not,  why?     What    allowance,   if   any,   should    be 
made  for  this? 

b.  Arterial  pressure. 

(5)  With  capillaries  1  to  6  open  and  tubes  7  and  8 
closed,  let  one  member  of  the  division  make  strong 
rhythmical  contractions  of  the  bulb  at  the  rate  of 
about  2  per  second.  Note  effect  on  manometer. 
Account  for  all  the  phenomena. 

c.  Venous  pressure. 

(6)  Note  the  effect  of  the  contraction  upon  the  venous 
manometer.  If  there  is  any  change  in  the  manome- 
ter, compare  in  rhythm  and  in  extent  with  the 
changes  in  the  arterial  manometer. 

d.  Relations  of  arterial  to  venous  pressure. 

(7)  Make  very  slow  contractions.      Note  results. 

(8)  Make  rapid,  strong  contractions.      Note  results. 

(9)  Make  rapid,  weak  contractions.      Note  results. 

(10)  Remove  the  clamps  from  vessels  7  and  8  (local 
dilatation  of  arterioks)  and  repeat  experiments  7,  8 
and  9,  noting  and  interpreting  results.  What  effect 
does  a  dilatation  of  arterioles  have  upon  venous 
pressure?  What  effect  does  it  have  upon  arterial 
pressure  ? 

e.  Pressure  formula. 
Let:   P   ^pressure. 

Pa  =arterial  pressure. 
Pv  =venous  pressure. 
H    ^strength  of  contractions. 

Rd  =  distal  resistance  beyond  point  of  observation. 
v     =velocity  at  point  of  observation, 
r      =radius  of  vessel  at  point  of  observation. 
How  many  of  the  following  formulae  will  your  observa- 
tions justify  ? 


CIRCULATION.  105 

1.  PaxH.  6.  PaxHxRd. 

2.  Pv  xH.  1.  Pa  xr2. 

3.  PaxRd.  8.  PaxHxRdXr-. 

4.  Pv  xRd.  9.  Pa  xv. 

5.  Pa  xPv.  10.  P     xHxRdXr2Xv. 

/.   Grafic  record  of  pulse  tracing  from  the  artificial  circula- 
tory system. 

With  the  recording  apparatus  used  in  Chapter  XXI  or 
with  a  sphygmograph,  or  better,  with  both  pieces  of 
apparatus,  make  tracings  of  the  pulsations  of  the 
arterial  tubes  "a"  and  "b."  (Fig.  17.)  Com- 
pare all  tracings  carefully  and  interpret  all  the 
features  of  the  record,  differentiating  the  essential 
from  the  nonessential,  as  before. 


XXIII.    The  pulse,  sphygmographs  and   sphygmograms. 

/.  Appliances. — A  sphygmograph;   tracing  slips;   a  fish-tail 

gas  jet,  or  kerosene  lamp. 
2.    Preparation. — Smoke  about  two  dozen  tracing  slips. 
j.    Operation. — That  the  sphygmograph  is  so  little  used  by 
the   general  practitioner  may  be  attributed  to  the  fact 
that  hurry   of  business,   or  some  other  cause,  has  hin- 
dered him  from  making  himself  thoroughly  conversant 
with  the  adjustment  and  use  of  the  instrument,  with  its 
limitations  and  with  the  interpretation  of  the  tracings. 
To  adjust  the  sphygmograph. 

First.  Let  the  observer  stand  with  his  right  foot  on  a 
chair.      This  brings  his  thigh  into  a  horizontal  position. 

Second.  Let  the  subject  stand  at  the  right  of  the  ob- 
server, resting  the  dorsal  surface  of  the  left  forearm  upon 
the  observer's  knee. 

Third.  Let  the  observer  with  pencil  or  pen  mark  the 
location  of  the  radial  artery. 

Fourth.  Let  the  observer  wind  the  clockwork  which 
drives  the  tracing  paper;  adjust  the  latter  in  readiness 
for  tracing;  rest  the  instrument  upon  the  subject's  arm 
with  its  foot  upon  the  radial  artery  and  adjust  the  posi- 
tion, tension  and  pressure,  in  such  a  manner  as  to  obtain 
the  maximum  amplitude  of  swing  of  the  tracing  needle. 
Take  the  tracing.  Fix. 
4.    Observations. 

a.    The  location,  etc.,  of  the  radial  artery. 

(1)  What  are  the  relations  of  the  radial  artery  at  the 
distal  end  of  the  radius  ? 

(2)  How  may  the  relations  vary? 

lOfi 


CIRCULATION.  107 

(3)  Is  there  any  variation,  among  the  members  of  the 
division,  in  the  location  of  the  radial  artery? 

(4)  May  excessive  muscular  development  affect  the 
ease  with  which  the  artery  may  be  located  and  its 
pulsations  studied? 

(5)  May  excessive  deposit  of  adipose  tissue  hinder 
the  observations  of  the  pulse? 

(6)  May  faulty  position  of  subject  or  of  his  clothing 
affect  the  pulse  ? 

7 he  digital  observation  of  the  radial  pulse. 

(7)  Feel  the  pulse  with  the  side  or  back  of  the  finger; 
then  with  volar  surface  and  tip  of  each  finger  of  each 
hand  and  note  the  finger  or  fingers  with  which  the 
feeling  is  most  acute.  It  will  be  wise  to  always  use 
these  fingers  in  all  tactile  examinations.  Their 
acuteness  of  feeling  will  increase  with  practice. 
One  may  thus  acquire  the  educated  touch — tactus 

EKUDITUS. 

(8)  How  much  may  be  learned  of  the  pulse  by  means 
of  the  touch  alone  ?  Observe  and  note  {a)  fre- 
quency; (o)  rhythm;  (V)  volume;  (d)  strength;  (/) 
compressibility.  (/)  May  anything  else  be  deter- 
mined by  this  method  ? 

The  Sphygmogram. 

(9)  Take  at  least  three  pulse  tracings  of  each  indi- 
vidual in  the  division,  {a)  Compare  the  tracings 
taken  from  one  individual;  if  they  differ,  determine 
the  cause  of  the  difference.  (^)  Compare  tracings 
of  different  members  of  the  division.  Determine,  if 
possible,  the  causes  of  the  differences. 

(10)  Do  variations  of  the  relations  of  the  artery  affect 
the  sphygmogram  ?  Does  the  adjustment  of  the 
instrument    affect    the    sphygmogram  ?     Does    the 


108  LABORATORY  GUJDE  IN  PHYSIOLOGY. 

elasticity  of    the   artery  affect    the   tracing  ?     How 

does  strength  or  rate  of  heart-beat  affect  it? 

Make  a  list  of  the  facts  regarding  the  condition  of  the 

circulatory  system  which  maybe  determined  with  the  help 

of   the   sphygmograph.      Make   a  list   of    the  precautions 

necessary  to  observe  in  the  use  of  the  sphygmograph. 


XXIV.     To  determine  the  general  influence  of  the  vagus 
nerve  upon  the  circulation.* 

/.  Appliances. — Operating  case,  (Appendix,  A-3);  a  pair 
of  curved,  blunt-pointed  shears,  or  better,  a  pair  of 
barber's  clippers;  a  rabbit  board;  large  sheet  of  heavy 
paper;  sealing  wax;  cotton;  ether;  thread;  1  Daniell 
cell;  inductorium;  vagus  electrodes;  2  Du  Bois  keys;  7 
wires;  stethoscope;  a  strong,  adult  rabbit. 
2.  Preparations. — Let  the  six  students  be  subdivided  into 
three  groups  of  two  students  each. 

Let  group  "«"  be  responsible  for  the  anaesthesia. 
Use  the  sheet  of  heavy  paper  to  make  a  conical  hood, 
whose  spiral  turns  may  be  held  in  place  with  sealing 
wax.  Place  a  wad  of  cotton  loosely  in  the  mouth  of 
the  cone. 

Let  group  ltb"  perform  the  operation.  Fix  the  rab- 
bit, back  downward,  upon  the  holder;  fix  the  nose  in 
special  holder  (see  Fig.  19);  with  the  barber's  clippers 
remove  the  hair  from  ventral  side  of  thorax  and  neck  ; 
make  hands  and  instruments  clean,  place  instruments 
in  a  shallow  basin  of  warm,  1  per  cent  carbolic  acid 
solution;  cut  two  or  three  ligatures  of  thread  and 
place  them  in  the  instrument  basin. 

Let  group  "  c  "  arrange  the  electrical  apparatus  for 
stimulation  of  the  nerves.  Fill  the  cell;  join  up  with 
contact-key  in  the  primary  circuit,  and  a  short  circuit- 
ing key  in  the  secondary  circuit.  Test  the  apparatus  to 
see  if  everything  is  in  order. 
J.    Operation. 

Group    "a."      (1)    Pour    2    cc.    or    3  cc.  of  sulphuric 

*Let  six  students  work  together. 

109 


110  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

ether  upon  the  cotton  in  the  cone;  place  the  cone  over 
the  rabbit's  nose;  observe,  and  note  carefully  every  step 
in  the  anaesthesia. 

(2)  Carefully  note  the  rate  of  the  heart  before  begin- 
ning anaesthesia. 

(3)  Keep  the  cotton  moist  with  ether;  watch  the 
respiration  and  pulse,  and  be  careful  not  to  give  the 
animal  too  much  and  interrupt  the  experiment. 

Group  "  i>."     Wash  the  clipped  surface  of  the  throat. 

After  the  rabbit  is  completely  anaesthetized,  make 
with  scissors  a  median  incision  through  the  skin,  be- 
ginning at  the  apex  of  the  sternum  and  cutting  anteriorly 


Fig.  19. 

for  about  5  or  6   cm.,  divide   the   subcutaneous  connec 
tive  tissue   over   the   middle  of   the   trachea.      Carefully 
separate    from  the   median   line  on   either   side  laterally 
the  subcutaneous  connective  tissue  with  the   associated 
adipose  tissue. 

How  many  pairs  of  muscles  come  into  view  ?  What 
two  muscles  approach  the  median  line  to  form  the  apex 
of  a  triangle  at  the  anterior  end  of  the  sternum  ?  Ob- 
serve a  pair  of  thin  muscles  lying  dorsal  to  the  muscles 
just  mentioned  and  joining  in  the  median  line  to  form  a 
thin  muscle  sheet  covering  the  trachea  on  its  ventral 
side?     What  muscles  are  these  ? 

Carefully  lift  up  the  median  edge  of  the  sterno  mas- 
toid  muscle  and   separate  with  the  handle  of  a  scalpel 


CIRCULATION.  Ill 

or  a  seeker  the  delicate  intermuscular  connective  tissue. 
A  blood  vessel  and  several  nerves  come  into  view. 

Is  the  blood  vessel  an  artery  or  a  vein  ?  How  many 
large  nerves  accompany  the  blood  vessel  ? 

Take  hold  of  the  sheath  of  the  vessel,  lift  it  up  and 
note  in  the  connective  tissue  accompanying  the  blood 
vessels  two  nerves,  one  large  and  one  small.  When  the 
artery  is  in  its  normal  position,  what  relation  do  these 
two  nerves  sustain  to  it?  Which  of  the  two  nerves  is 
external  and  which  is  dorsal  to  the  bloodvessel?  Which 
is  in  close  relation  to  the  artery?  What  is  the  name  of 
each  of  the  nerves? 

In  preparing  the  nerve  for  stimulation  one  should 
neither  grasp  it  with  the  forceps  nor  with  the  fingers. 
It  may  be  separated  from  the  delicate  connective  tissue 
in  which  it  lies  by  use  of  a  blunt  seeker.  Far  better 
than  any  metallic  instrument  is  a  small  glass  rod  drawn 
to  a  point,  curved  and  rounded  in  the  Bunsen  lamp 
(see  Fig.  11- A).  Prevent  the  tissues  drying  up  by 
occasionally  pressing  them  lightly  with  pledgets  of 
cotton  moistened  with  normal  salt  solution. 

Adjust  the  electrode  carefully  upon  the  vagus  and  see 
that  no  unnecessary  tension  is  allowed  to  be  exerted 
upon  the  nerve.  It  is  usually  necessary  to  hold  the 
electrode  in  place  during  the  observations. 

Observations. 
a.  Anesthesia.      (Observations  by  Group  "a.") 

(1)  Are  you  able  to  make  out  different  stages  in  anaes- 
thesia? 

(2)  How  many  stages  did  your  animal  manifest? 

(3)  Give  the  characteristics  of  each  stage. 

(4)  What  effect  did  the  ether  have  upon   the  rate  of 
heart  beat? 

(5)  What  effect  did  the  ether  have  upon  the  respira- 
tion? 


1 1 2  LABOR  A  TOR  Y  GUIDE  IN  PHYSIO  LOG  Y. 

b.    The    stimulation     of    the    vagus.        (Observations     by 
Group  "  c. ") 

(6)  Stimulate  moderately  one  vagus.  Note  with  a 
stethoscope  whether  the  rate  of  the  heart  is  in- 
creased. 

(7)  Cut  both  vagi  high  up  in  the  neck.  Note  the 
rate  of  heart  beat  at  intervals  of  five  minutes  for 
twenty  minutes,  allowing  the  rabbit  to  partially 
recover  from  the  anaesthesia. 

(8)  Stimulate  one  vagus.  Compare  the  result  with 
that  obtained  under  experiment  (6). 

(9)  Will  very  strong  stimulation  bring  the  heart  to  a 
standstill  ? 

(10)  If  the  heart  was  brought  to  a  complete  stand- 
still by  the  stimulation,  will  it  start  up  again  spon- 
taneously when  the  stimulus  is  removed?  Will  the 
rate  reach  the  degree  of  acceleration  observed  in 
experiment  (7)? 

(11)  Sum  up  the  observations  into  a  concise  state- 
ment as  to  the  influence  of  the  vagus  upon  the 
heart. 

Note:   Dispatch  the  rabbit  with  chloroform. 


D.   RESPIRATION. 


IX.  a.   External  respiratory  movements,     b.    Intra=thor= 
acic  pressure,     c.  Intra=abdominal  pressure. 

/.  Appliances. — Operating  case;  clippers;  rabbit  board; 
rabbit;  cone  for  anaesthesia;  ether;  kymograph;  cardio- 
graph, which  may,  in  this  case,  be  called  a  rabbit  stetho- 
graph;  three  recording  tambours;  10  cm.  of  glass  tubing. 
3  mm.  lumen;   rubber  tubing  to  match;   chronograph. 

2.   Preparation.  , 

(1)  Fix  and  anaesthetize  rabbit. 

(2)  Clip  ventral  aspect  of  rabbit's  thorax  and  abdomen. 

(3)  Prepare  thoracic  and  abdominal  cannulas  by  drawing 
the  glass  tube  slightly  in  the  center,  cutting  diagonally 
at  the  middle,  smoothing  diagonally  on  an  emery  stone. 

(4)  Join  a  30  cm.  piece  of  rubber  tubing  to  each  cannula 
at  the  larger  end,  and  clamp  it  near  the  cannula. 

J.    Operation. 

a.  External  respiratory  movements. 

Place  the  button  of  the  rabbit  stethograph  upon  the 
ventral  surface  of  the  rabbit  as  near  as  possible  over  the 
junction  of  the  diaphragm  with  the  body  wall,  and  a  lit- 
tle to  the  right  or  left  of  the  median  line.  So  adjust  the 
stethograph  as  to  obtain  the  maximum  excursion  of  the 
recording    lever.     The  stethograph  may  be  held  in  posi- 

113 


114  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

tion  through  the  agency  of  a  clamp  and  support;  some- 
times, however,  better  results  may  be  secured  by  holding 
the  stethograph  in  the  hands,  supporting  the  wrists  on 
the  edge  of  the  rabbit  board. 

b.  Intrathoracic  pressure. 

Locate  an  intercostal  space  to  the  right  of  the  ster- 
num and  opposite  its  middle  point.  Make  an  incision 
0.  5  cm.  long,  parallel  with  the  intercostal  space  and  1  cm. 
from  the  sternum.  Dissect  through  the  intercostal  mus- 
cies,  taking  care  not  to  cut  the  pleura.  Insert  the  point 
of  the  glass  cannula  into  the  wound,  press  it  carefully 
through  the  pleura  into  the  right  pleural  cavity. 

Join  the  rubber  tube  to  a  recording  tambour  and  un- 
clamp.  Slowly  and  gently  manipulate  the  cannula  until 
there  is  evident  communication  through  the  lumen  of  the 
cannula  and  tube  from  the  pleural  cavity  to  the  tambour. 

So  adjust  the  cannula  that  the  recording  lever  makes 
the  maximum  excursion.  Bring  the  levers  into  such  a 
relation  to  the  kymograph  that  the  tracing  point  of  the 
stethograph  lever  shall  be  vertically  over  that  of  the 
lever  which  is  to  record  intra-thoracic  pressure,  and  about 
two  centimeters  from  it. 

c.  Intra=abdominaI  pressure. 

Make,  in  the  median  line  of  the  abdomen,  a  one-cen- 
timenter  incision,  limited  anteriorly  by  the  xiphoid  ap- 
pendix. After  partially  dissecting  through  the  abdom- 
inal wall  insert  the  cannula  into  the  incision  and  care- 
fully press  it  through  the  peritoneum.  If  one  push 
the  cannula  between  the  diaphragm  and  liver  he  will 
usually  be  successful  in  getting  the  free  end  of  the  can- 
nula into  an  open  space.  Care  should  be  taken  not  to 
wound  the  liver.  Take  tracing  as  in  b. 
4.    Observations. 

a.   Exierfial  respiratory  movements. 


RESPIRATION.  115 

(1)  During  one  revolution  of  the  drum — 5  minutes — 
note  the  rate  and  rhythm  of  the  respiratory  move- 
ments as  recorded  by  the  stethograph,  and  chrono- 
graph. 

(2)  Does  the  stethogram  show  anything  more  than 
rate  and  rhythm  ? 

(3)  What  phase  of  a  respiratory  cycle  does  a  rise  of 
the  lever  indicate? 

(4)  What  is  the  relative  duration  of  inspiration  and 
expiration  as  indicated  by  the  stethogram? 

(5)  Does  the  stethogram  indicate  any  variation  indif- 
ferent parts  of  the  inspiratory  act  ?  Of  the  expira- 
tory act  ? 

(6)  Differentiate  the  essential  from  the  nonessential 
in  the  stethogram  and  determine  as  far  as  may  be, 
the  cause  of  each. 

Intra-thoracic  pressure. 

Trace  upon  the  drum  a  stethogram  and  chronogram 
as  well  as  an  intra-thoracic  pressure  record,  taking 
care  that  the  tracing  points  of  the  recording  tam- 
bours are  in  a  vertical  line. 

(7)  Does  the  rhythm  of  varying  pressure  correspond 
to  the  rhythm  of  the  respiratory  movements  ? 

(8)  If  so,  does  that  necessarily  establish  between  them 
the  relation  of  cause  and  effect? 

(9)  What  change  of  pressure  is  indicated  by  the  rise 
of  the  pressure  lever? 

(10)  What  movement  of  the  pressure  lever  corre- 
sponds to  a  rise  of  the  stethograph  lever? 

(11)  What  is  the  condition  of  intrathoracic  pressure 
during  inspiration?     During  expiration? 

(12)  Stop  the  entrance  of  air  into  the  respiratory  pas- 
sages by  closing  the  rabbit's  nostrils.  What  effect 
does  this  have  upon  the  respiratory  movements? 


116  LABOR  A  TOR  V  G  UIDE  IN  PHYSIOL  OGY. 

(13)  Is  the  intra-tboracic  pressure  affected  by  the  ex- 
periment ?     If  so,  explain  the  effect. 

(14)  If  two  phenomena  correspond  perfectly  in  their 
cycles,  and  if  a  variation  of  one  is  always  accom- 
panied by  a  variation  in  the  other,  can  there  be  any 
reasonable  doubt  that  they  sustain  to  each  other  the 
relation  of  cause  and  effect  ? 

(15)  Is  one  of  the  phenomena  in  question  the  cause 
of  the  other?  If  so,  state  which  is  the  cause  and 
establish  your  position. 

To  measure  intra  thoracic  pressure. 

(16)  Clamp  the  rubber  tube  of  the  pressure  appa- 
ratus. Replace  the  recording  tambour  v  ith  a  water 
manometer.      Unclamp. 

Is  the  pressure  during  inspiration  positive  or  negative, 
and  how  much  ? 

(17)  Is  the  pressure  during  expiration  positive  or 
negative,  and  how  much  ? 

(18)  If  the  whole  apparatus  were  filled  with  water 
instead  of  air  and  water,  would  it  make  any  essen- 
tial difference  in  the  result  ?  What  effect  do  the 
variations  of  the  intrathoracic  pressure  have  upon 
the  circulation  ?     Upon  the  respiration  ? 

c.   Intra-abdominal  pressure. 

Trace  upon  the  drum  a  stethogram  and  chronogram  as 
well  as  a  record  of  the  intra  abdominal  pressure. 

(  19)  Does  the  rhythm  of  varying  intra  abdominal 
pressure  correspond  with  the  rhythm  of  the  respira- 
tory movements  ? 

(20)  With  what  phases,  respectively,  of  the  respira- 
tion do  rise  and  fall  of  the  intra-abdominal  pressure 
correspond  ? 

('21)  What  influence  upon  the  circulation  would  rise 
of  the  intra-abdominal  pressure  exert? 


RESPIRATION  117 

(22)  Make  a  quadruple  tracing:     stethogram,  chrono 
gram,  intra-thoracic   pressure   and   intra-abdominal 
pressure. 

(23)  Sum    up  the  work  of    the   day  in  a  series  of  con 
elusions. 

(24)  Dispatch  the  rabbit  with  chloroform,  noting  the 
respiratory  changes  induced  by  the  lethal  dose  of 
chloroform  gas. 


XXVI.    Respiratory  movements  in  man.     a.  The  stetho= 

graph,     b.  The  thoracometer.     c.  The  belt= 

spirograph,     d.  The  stethogoniometer. 

/.    Instruments. — Besides  a  kymograph  and  a  chronograph, 
the  following: 
Stethograph. — An  instrument  for   recording    graphically 

the  movements  of    the  chest-walls   [Gould]. 
Thoracometer.  —  An     instrument     for      measuring   (and 
recording)  the  movements  of  the  chest- walls  [Gould]. 
Belt-spirograph. — An    appliance  for    recording    respira- 
tory changes  in  thoracic  or  abdominal  girth. 
Stethogoniometer. — An     instrument     for    measuring    the 
curvature  of  the  chest  [Gould]. 
2.  Appliances  needed  in  the  adjustment  and  use  of  these 
instruments. — Heavy  base  support;  three  large  clamp 
holders;  iron  rod,  8  or  10  mm.  in  diameter  and  50  cm. 
long;  two  wooden  or  iron  rods,  1  cm.  in  diameter  and 
40  c.  m.  long  ;  a  receiving  tambour  ;  a  recording  tambour, 
with    support;    two  medium    clamp  holders;    two    uni- 
versal   clamp    holders;    simple    myograph;    \y2    meter 
fine  fish  cord;  two  pulleys. 
J.   Preparation. — For  construction  of  apparatus  see  Appen- 
dix A,  10-13. 

Adjustment  of  the  apparatus. 
a.  The  Stethograph. 

Clamp  the  center  of  the  iron  rod  to  the  heavy  base 
support.  Clamp  the  wooden  rods  to  the  iron 
rods  so  that  they  will  extend  out  to  one  side  of  the 
iron  rod  in  a  horizontal  plane.  Figure  20  shows  the 
stethograph  ready  for  use. 

118 


RESPIRATIOX. 


119 


Let  a  member  of  the  division  remove  all  clothing 
above  the  waist  and  be  the  subject  of  observation  for 
the  other  members.  In  making  observations  with  the 
stethograph  the  subject  should  sit  with  his  back  or 
side  to  the  table.  The  observer  may  readily  adjust 
the  stethograph  to  record  the  changes  of  any  lateral 
or  dorso-ventral  diameter  of  the  thorax.  For  all 
observations  upon  the  respiratory  changes  in  the 
thorax,  the  subject  should  keep  the  parts  of  the  body 
symmetrically  disposed. 


Fig.  20. 

Observations. 
\\)   How  much  may  be  learned  of   man's  respiratory 
movements  by  simple  inspection?     Make  a  careful 
enumeration  and  record. 

(2)  Adjust  the  stethograph  and  make  a  record — a 
stethogram — of  the  changes  of  the  lateral  diameter 
of  the  thorax  at  the  ninth  rib. 

Does  the  stethograph  show  more  than  could  be 
learned  from  inspection?     If  so,  what? 

(3)  Take  a  stethogram  of  the  lateral  diameter  at  the 
sixth  rib.  How  does  it  differ  from  the  ninth  rib 
stethogram  ?     Account  for  the  difference. 


1 20  LA  BORA  TOR  Y  G  UIDE  IN  PH  YSIOLOG  Y. 

(4)  Take  a  stethogram  of  the  dorso  ventral  diameter 
of  the  thorax  over  the  lower  end  of  the  gladiolus. 
Compare. 

(5)  Take  a  lateral  ninth  rib  stethogram  while  the 
subject  reads  a  paragraph;  sighs;  coughs;  and 
laughs.     Account  for  the  peculiarities. 

(6)  Take  a  lateral  ninth  rib  stethogram  after  the  sub- 
ject has  taken  vigorous  exercise.  What  changes 
are  to  be  noted  ? 

(7)  After  a  similar  series  of  stethograms  have  been 
taken  for  others,  compare;  determine  the  essential 
features;  give  causes  of  these. 

(8)  Seek  the  causes  of  the  difference  which  exist  be- 
tween stethograms  of  different  individuals.  May 
they  be  accounted  for  by  stature,  condition,  occupa- 
tion or  habit? 

b.  The  thoracometer.  —  Remove  from  the  stethograph 
the  wooden  rod  which  bears  the  receiving  tambour, 
and  slip  the  iron  rod  of  the  apparatus  described  in 
Appendix  A- 11  into  the  same  place  with  the  button 
inward.  The  accuracy  of  the  apparatus  is  increased 
if  the  heavy  support  which  bears  the  spiral  spring, 
just  fixed  in  position,  bear  also  the  recording  lever. 
Use  a  simple  myograph  lever  which  may  be  clamped 
to  the  support.  The  cord  which  runs  ever  the  pulley 
beneath  the  spring  must  change  direction  at  least 
twice  after  leaving  the  first  pulley.  One  will  need 
two  more  pulleys  such  as  the  one  described  in  the  ap- 
pendix. They  may  be  held  in  position  by  clamp 
holders.  If  one  use  a  horizontal  drum,  however,  the 
cord  may  pass  from  the  first  pulley  direct  to  the  lever. 
In  either  case  one  would  need  to  pass  an  elastic  band 
around  the  short  arm  of  the  myograph  lever  in  such  a 
way  as  to  draw  the  lever  in  a  direction  opposite  to  that 


RESPIRA  7  7  ON.  121 

given  it  by  the  spiral  spring.  In  every  case  the  elas- 
ticity of  the  elastic  band  must  be  less  than  that  of  the 
spiral  spring,  otherwise  the  rubber  button  would  not 
follow  the  movements  of  the  thoracic  wall.  So  adjust 
the  apparatus  that  every  movement,  however  slight, 
of  the  button  will  be  instantly  responded  to  by  the 
lever. 
1 4')    Observations. 

(0)  Carefully  measure  the  arms  of  the  lever  to  deter- 
mine how  much  the  tracing  point  of  the  lever  will 
move  for  every  millimeter  that  the  button  moves. 

(10)  When  the  button  is  pressed  outward  in  inspira- 
tion what  direction  does  the  lever  move? 

(11)  Take  tracings  of  the  changes  in  the  dorso  ven- 
tral diameter  at  the  level  of  the  nipples.  Deter- 
mine by  measuring  the  tracing  how  much  the 
dorso  ventral  expansion  is.  What  is  the  average 
expansion  during  normal,  quiet  breathing  ?  What 
is  the  expansion  during  forced  respiration  ? 

(12)  Make  a  similar  series  of  observations  on  the 
lateral  diameter  in  the  plane  of  the  nipples. 

(13)  Repeat  observations  on  the  lateral  ninth  rib 
diameter. 

c.  The  beIt=spirograph.—  Substitute  for  the  rod  of  the 
thoracometer  which  bears  the  button  and  spring,  a 
plain  wooden  or  iron  rod.  Place  the  belt-spirograph 
around  the  subject  at  any  level  of  the  body,  whose 
varying  girth  is  to  be  observed.  The  fish  cord  used 
in  the  previous  experiment  may  be  transferred  to  this 
instrument.  Tie  one  end  into  the  eye  in  pulley  No.  1, 
pass  it  over  the  other  pulleys  and  to  the  lever;  the 
horizontal  bars  may  be  raised  to  the  axillae  and  will 
serve  to  steady  the  subject.  The  expansion  in  girth  of 
thorax  is  so  great  that  it  may  be   found  necessary  to 


122  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

change  the  relative  lengths  of  the  lever- arms  to  avoid 
too   great    an   excursion  of   the   writing    point    of    the 
lever. 
(«£")      Observations. 

(14)  How  many  millimeters  will  the  point  of  the 
lever  rise  or  fall  for  every  centimeter  that  the  girth 
increases  ? 

(15)  What  is  the  average  expansion  of  the  thorax 
during  normal  quiet  breathing? 

(16)  During  five  minutes — 75  or  80  respirations — are 
all  of  the  respirations  practically  the  same  or  are 
there  occasionally  deeper  breaths?  If  the  latter  is 
observed  is  there  any  regularity  in  the  occurrence 
of  deeper  respirations  ?  How  may  occasional  deep 
respirations  be  accounted  for? 

(17)  Let  the  subject  make  a  series  of  forced  respira- 
tions. What  is  the  maximum  expansion  ?  What  is 
the  average  expansion  of  the  series? 

d.  The  stethogoniometer. 

This  instrument  is  described  in  Appendix  A  13.  Its 
purpose  is  to  record  the  outline  of  any  horizontal 
section  of  the  thorax,  though  it  could  be  used  as  well  for 
tracing  the  periphera  of  the  abdomen,  of  the  head, or  of  a 
limb.  To  use  the  stethogoniometer  for  the  purpose  here 
intended  let  the  subject  sit  beside  a  table  upon  a 
stool  adjustable  for  height.  So  adjust  the  stool  as  to 
bring  the  circumference  of  the  thorax  to  be  observed 
even  with  the  upper  surface  of  the  table.  Fix  the 
point  c,  of  the  instrument,  to  the  table.  Let  the  ob- 
server locate,  with  pen  or  pencil,  upon  the  side  of  the 
subject  distal  from  the  table,  a  point  which  shall  serve 
as  a  starting  point. 

When   the  point  b,  of  the    instrument,   rests  upon 
this    point    of    the    subject's  thorax    the    instrument 


RESPIRATION,  123 

should  be  well  extended,  somewhat  more  than  repre- 
sented in  the  figure.  Fix  a  sheet  of  paper  to  the  table 
under  the  recording  pencil  at  a.  To  take  a  graphic 
record  of  the  contour  of  the  thorax,  proceed  as  follows: 

(18)  {a)  Let  the  observer  place  the  tracing  point  b 
upon  the  "starting  point"  in  the  distal  side  of 
the  thoracic  perimeter. 

(h)  Sweep  the  tracing  point  quickly  around  one- 
half  the  perimeter  to  a  point  approximately  oppo- 
site to  the  starting  point. 

(/)  Rotate  the  curved  arm  of  the  instrument  upon 
its  axis  bx,  through  180°. 

(d)  Sweep  the  tracing  point  around  the  other  one- 
half  of  the  perimeter  to  the  starting  point. 

(<?)  The  movements  of  the  tracing  point,  b,  in  the 
horizontal  plane  have  been  faithfully  recorded 
upon  the  sheet  of  paper  by  the  recording  pencil 
at  a.  It  is  hardly  necessary  to  remind  the  student 
that  the  subject  must  remain  motionless  during 
the  observation. 

(19)  Take  a  thoracic  perimeter  with  the  chest  in  re- 
pose. Measure  different  diameters  of  the  tracing 
and  multiply  by  five  to  reduce  to  actual  measure- 
ments. 

(20)  Take  a  tracing  at  end  of  forced  expiration;  at 
end  of  forced  inspiration.     Compare  diameters. 

(21)  Make  a  series  of  these  tracings  for  different  in- 
dividuals.     Compare. 

(22)  Formulate  conclusions. 


XXVII.  Respiration  in  man;  lung  capacity  and  strength 

of   inspiration   and    expiration;   chest   measure- 

ments;  the  preservation  of  the  data. 

/.  Instruments. — Spirometer;  pneo-manometer;  meter  tape; 
steel  calipers;  standard,  with  horizontal  arm  for  meas- 
uring height;  scales  for  taking  weight. 

2.    Observations. 

(1)  Test  with  the  spirometer  the  lung  capacity  of  each 
member  of  the  division.  May  differences  in  lung  ca- 
pacity be  accounted  for  by  difference  in  stature,  condi- 
tion, occupation  or  habit? 

(2)  Take  with  the  tape  the  girth  of  chest  over  the  nipples 
in  a  plane  at  right  angles  with  the  axis  of  the  thorax. 

(a)  With  chest  in  normal  repose. 

(b)  At  the  end  of  forced  expiration. 
(V)   At  the  end  of  forced  inspiration. 

(3)  Take  the  girth  of  chest  over  the  juncture  of  the 
ninth  rib  with  its  cartilage,  holding  the  tape  in  a  plane 
at  right  angles  with  the  axis  of  the  thorax. 

(a)  With  the  chest  in  repose. 

(b)  At  the  end  of  forced  expiration. 
(7)   At  the  end  of  forced  inspiration. 

(4)  With  the  calipers  measure  the  dorso-ventral  diameter 
at  the  level  of  the  nipple,  holding  the  calipers  in  a 
plane  perpendicular  to  the  axis  of  the  thorax. 

{a)   Normal,  (b)  after  expiration,  (V)  after  inspiration. 

(5)  Take  the  lateral  diameter  in  the  nipple-plane. 

(a)   Normal,  (b)  after  expiration,  (7)  after  inspiration. 

(6)  Take  the  lateral  diameter  at  the  ninth  rib. 

(a)   Normal,  (b)  after  expiration,  (<r)  after  inspiration. 

124 


RESPIRATION.  125 

(7)  Test  with  the  pneo  manometer  the  force  of  inspira- 
tion and  expiration.  (Appendix,  A  14).  Let  each 
member  of  the  division  test  with  the  pneo-manometer 
the  maximum  positive  pressure  which  he  is  able  to 
produce  in  the  respiratory  passages  during  expiration. 

(8)  Test  with  the  same  instrument  the  maximum  nega- 
tive pressure  which  each  individual  can  produce 
during  inspiration. 

(9)  Does  the  face  become  red  in  either  of  these  tests? 
If  such  is  uniformly  observed,  account  for  it. 

(10)  The  preservation  of  data.  Experience  has  shown 
that  when  data  are  to  be  preserved  for  subsequent  use 
in  the  comparison  of  one  class  of  individuals  or  cases 
with  another,  it  is  very  much  more  economical  in  time 
to  record  the  data  upon  cards. 

For  the  above  data  one  may  use  such  a  card  as  is 
appended  to  this  chapter. 

In  addition  to  the  measurements  above  given  record 
upon  the  cards  the  weight,  the  height,  the  bodily  condi- 
tion of  the  individual,  and  especially  whether  the  indi- 
vidual has  lived  in  a  hilly  or  in  a  flat  country,  and 
whether  he  has  been  active  or  inactive. 

Name 

Age Weight 

Condition:   Fat,  medium  or  lean. 

Muscular  development 

Previous  occupation 

Home Flat  or  hilly  region. 

Habit:     Inactive,  active,  (tennis,  bicycle ) 

Lung  capacity Height 

Girth  of  chest  in  repose 

Girth  of  chest  at  end  of  forced  inspiration 

Girth  of  chest  at  end  of  forced  expiration 

Girth  of  chest  at  ninth  rib,  repose 


126  LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Girth  of  chest  after  forced  inspiration 

Girth  of  chest  after  forced  expiration 

Diameter  of  chest  dorso-ventral,  in  repose 

full empty 

Diameter  of  chest,  lateral,  in  repose full 

empty 

Observer 

Date 


XXVIII.     The  evaluation  of  anthropometric  data. 

A  large  proportion  of  the  problems  that  the  medical 
man  has  to  solve  involves  the  finding  of  averages  of  a 
large  number  of  observations.  This  is  sure  to  be  true  of 
all  anthropometric  problems.  In  the  course  of  the  pre- 
ceding lesson  valuable  anthropometric  data  were  collected 
and  recorded  upon  cards.  The  value  of  this  material  is 
purely  potential.  Before  the  data  will  furnish  a  basis  for 
drawing  conclusions  it  is  necessary  to  subject  it  to  a  pro- 
cess of  evaluation.  This  process  consists,  first,  in  group- 
ing; second,  in  getting  the  average  or  the  median  value 
for  each  measurement;  and,  third,  in  graphically  repre- 
senting the  averages.  In  the  previous  lesson  the  observer 
noted  upon  each  card  whether  the  subject  had  lived  in  a 
hilly  or  in  a  flat  country;  further,  whether  he  had  led  a 
physically  active  or  inactive  life.  This  gives  one  an  op- 
portunity for  four  groups  when  the  cards  from  the  whole 
class  are  collected. 

Group   I.  Active  men  from  a  hilly  country. 
"       II.  "  "  "  flat 

"     III.  Inactive  "  "  hilly         " 

"      IV.  "  "  "         flat  " 

Until  recently  it  has  been  customary  to  simply  write 
the  data  for  any  group  in  columns  and  "strike  an  average" 
of  each  column.  If  there  are  only  10  to  20  or  30  individ- 
uals in  each  group  this  method  does  not  entail  the  unnec- 
essary expenditure  of  much  energy,  but  it  is  not  reliable; 
for   one  "  giant  "  or  "  dwarf  "  in  any  group  would  vitiate 

127 


128 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


the  whole  result.  If  thtre  aie  100  or  1000  individ 
uals  in  a  group,  then  the  use  of  the  old  method  of  finding 
the  arithmetrical  average  is  exceedingly  wasteful  of  both 
time  and  energy.  It  must  be  added,  however,  that  when 
the  number  of  observations  is  large  the  chances  are  that 
there  will  be  as  many  dwarfs  as  giants,  thus  making  the 
average  approximate  closely  the  median  value.  It  is  the 
latter  that  we  are  seeking,  viz.:  the  median  value;  this 
may  be  defined  as  that  value  which  is  so  located  in 
the  whole  series  of  observations,  in  a  single  measurement 
of  any  group,  that  there  are  as  many  below  it  as  above  it, 
i.  e.,  that  t'he  numbers  of  values  which  it  exceeds  is  equal 
to  the  number  of  values  which  exceed  it. 

Let  us  take  a  concrete  case.  In  a  group  of  3!6  seven- 
teen-year-old boys  certain  physical  measurements  were 
recorded  upon  individual  cards.  Let  us  take  for  an  ex- 
ample the  gir ill  of  head  recorded  in  centimeters  and  tenths. 
Instead  of  writing  in  a  column  the  316  head  girths,  each 
expressed  in  three  figures,  adding  and  averaging,  let  us 
adopt  the  new  method  first  suggested  by  the  Belgian  as- 
tronomer and  anthropologist,  Quitelet,  and  later  elabo- 
rated by  Gaiton,  the  London  anthropologist.*  Arrange 
the  cards  in  piles,  placing  in  one  pile  all  of  the  cards 
having  girth  of  head  51+  centimeters,  in  another  pile  all 
having  52— |—  centimeters,  and  so  on.  In  the  case  in  ques- 
tion it  was  found  that  the  316  cards  were  quickly  distrib- 
uted, falling  into  the  following  groups: 


GIRTH   OF  HEAD. 


NO.   OF  OBSERVATIONS 

(No.  of  Cards.) 


51+ 


52+ 

7 


53+54+ 


17 


4! 


55+ 


70 


56+ 

71 


57+ 


(in 


58+ 


29 


.-,9+60+ 

in 


*  For  a  more  extended  explanation  and  development  of  this  method 
than  given  in  this  chapter  see  also  "  Chnnges  in  the  Proportions  of  the 
Human  Body" — Hall.     Journal  of  i he  Attlhi opological Institute  of  Great 

Britain  and  Ireland.      London,  August,  1895. 


RESPIRATION.  129 

The  problem  is  to  find  the  value  of  the  median  measure- 
ment or  the  median  value.  There  are  158  values  below 
the  median  and  as  many  above. 

First.  To  locate  the  median  observatio?i  :  This  is  equiv- 
alent to  saying — find  in  the  lower  series  of  numbers 
(1-7  17,  etc.)  the  158th  observation  from  either  end.  It 
must  be  located  in  the  pile  of  cards  which  numbers  74. 
This  group  may  be  called  the  median  group.  But  where  in 
this  group  is  the  median  observation  located?  In  order  to 
determine  this,  add  the  groups  at  the  left  of  the  median 
group,  these  may  be  called  the  minus  groups,  the  values 
which  they  represent  being  less  than  that  of  the  median 
group.  l  +  7-|-l7-H  1  +  70=136.  To  this  sum  one  must 
add  22  observations  from  the  median  group  to  make  158. 
The  median  observation  is  then  located  in  the  median 
group,  22  points  from  the  left. 

Second.  To  evaluate  the  median  observation  we  must 
take  it  for  granted  that  the  74  observations  of  the  median 
group  are  evenly  distributed  over  the  distance  between  56 
cm.  and  57  cm.  That  being  the  case  the  median  value 
would  be  56ff  cm. 

Let  us  put  a  general    proposition  in  the  form  of    an  al 
gebraic  formula. 

Let  M  ==  the  number  of  observations  in  the  median 
group. 

Let  n  =  the  total  number  of  observations. 

2p  =  the  sum  of  the  plus  groups. 

2m  =  the  sum  of  the  minus  groups. 

a  =  the  minimum  value  of  the  median  group. 

d  =  the  arithmetric  difference  in  the  minimum  values 
of  the  groups. 

/i  =  the  median  value  to  be  determined. 

d(-f-2m)                                     d(^i--Sp) 
Then  /i  =  a  -\ ^ or  fi  =  a  +  d = '- 


130  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

Apply  this  formula  to  the  case  taken   for  example  : 

1   (M       _    13G  ) 
1,  =  56  +  -^^ -=56.3. 

or 

1    (  ™       _     106) 
ft  —  51 ^ '-=  ol  —  0.703  =  56.3. 

After  one  has  found  the  median  value  for  each 
measurement  in  each  group,  these  may  be  tabulated  and 
the  values  compared.  When  the  table  of  median  values 
is  large  it  is  almost  necessary  to  carry  the  work  of  reduc- 
tion a  step  farther  and  represent  these  values  graphically 
in  a  chart.  Another  opportunity  will  be  used  for  giving 
the  methods  used  in  the  graphic  representation  of  statis- 
tical tables. 

The  table  which  results  from  the  data  collected  in 
connection  with  the  previous  lesson  is  not  so  large  but  that 
the  observer  can  practically  comprehend  the  whole  at  a 
glance. 

Our  grouping  enables  us  to  answer  the  following  ques 
tions  : 

First.  Has  general  physical  activity  any  essential  in- 
fluence in  the  development  of  the  respiratory  organs  and 
function  ? 

Second.  Is  the  climbing  of  hills  during  early  life  a 
factor  in  the  development  of  the  respiratory  organs  and 
function  ? 

If  both  of  these  questions  may  be  answered  affirma- 
tively then  one  would  expect  to  find  that  the  median  values 
of  group  I,  (active  individuals  from  a  hilly  country)  uni- 
formly exceed  the  values  of  group  II;  and  that  those  of 
group  III  uniformly  exceed  those  of  group  IV,  but  that 
the  median  values  of  group  II  may  or  may  not  exceed 
those  of  group  III. 

The  following  conclusions  are  quoted  from  a  student's 
note  book  : 


RESPIRA  TION.  131 

(1)  "  Every  measurement  of  the  •  median  '  active  man 
is  greater  than  the  corresponding  measurement  of  the 
'  median  '  inactive  man." 

(2)  "Every  measurement  of  the  median  active  man 
from  a  hilly  country  is  greater  than  the  corresponding 
measurement  of  the  median  active  man  from  a  flat  coun- 
try." 

(3)  "But  the  active  flat  country  men  exceed  in  their 
median     measurements    the    inactive    hill    country   men, 
therefore,  physical  activity  isa  stronger  factor  in  the  devel 
opment  of    respiratory  organs  than  is    the  topography  of 
the  habitat." 


XXIX.     The  action  of   the  diaphragm. 

Appliances. — Operating  case  ;  clippers  ;  rabbit  board,  or 
dog  board  ;  rabbit  or  dog  ;  ether  ;  ether  cone  ;  absorbent 
cotton  ;  kymograph  ;  chronograph  ;  recording  tambour; 
beaker  with  warm  water  ;  medicine  dropper  or  bulb.  (If 
a  dog  be  used,  the  medicine  dropper  will  not  be  large 
enough,  its  place  may  be  taken  by  a  soft  spherical  rub- 
ber bulb  about  2  cm.  in  diameter.)  Inductorium,  1  cell, 
2  keys,  vagus  electrode,  5  common  wires  and  2  fine 
wires.  Sometimes  the  bulbs  mentioned  above,  and  usu- 
ually  used  for  this  purpose,  are  not  satisfactory.  Very 
good  results  may  be  gotten  by  using  a  piece  of  glass  rod, 
which  has  been  rounded  at  one  end  and  sharpened  at 
the  other,  as  a  lever.  (Fig.  21.)  The  rounded  end  is 
passed  through  the  abdominal  wall  and  rests  against  the 
diaphragm,  (d).  The  point  is  inserted  into  the  cork 
button  of  a  tambour.  Any  contraction  of  the  dia- 
phragm presses  the  round  end  down,  the  body  wall 
serves  as  a  fulcrum  (/),  the  point  is  pressed  up  and  the 
lever  of  the  recording  tambour  rises. 

Preparation. — Fix  the  animal  to  the  board;  anaesthetize; 
clip  anterior  median  region  of  abdomen.  Put  the  bulb 
into  the  warm  water,  join  the  glass  tube  of  the  bulb  to  the 
recording  tambour  through  a  rubber  tube.  This  appa- 
ratus thus  joined  may  be  called  a  phrenograph  and  its 
record  a  phrenogram. 

Set  up  electrical   apparatus  with   short-circuiting   key 
in  secondary  coil. 

Operation. — From  the  posterior  extremity  of  the 
xyphoid  appendix  make  a  median   incision  through  the 

132 


KESPIRA  TION. 


133 


abdominal  walls.  If  the  lever  be  used  the  incision 
should  be  just  large  enough  to  admit  the  lever,  and 
should  be  located  in  the  angle  between  the  xyphoid  and 
the  costal  cartilages  on  the  right  side. 

Clamp  with  the  serre-fines  any  small  vessels  which  may 
be  oozing.  After  having  clamped  the  rubber  tube,  which 
connects  the  bulb  to  the  tambour,  carefully  insert  the 
warm,  wet  bulb  between  the  diaphragm  and  the  liver 
The  liver  will  usually  afford  sufficient  resistance  to  cause 
alternate  compression  and  relaxation  of  the  bulb  and  a 
consequent  rise  and  fall  of  the  recording  lever;  if  such 
be  not  the   case,  the  liver   may  be  held  in   place  by  two 


Fig.  21. 

Fig.  21.     Glass  lever  for  transmitting  movements  of  the  diaphragm  (</) 

to  the  receiving  tambour.     The  abdominal  wall  forms  the 

fulcrum  (/")  of  the  lever. 


fingers  inserted  through  the  incision.      In  the  meantime 
let  another  member  of    the  division  dissect  out  the  left 
phrenic  nerve.     Fig.  22  shows  the  relation  of  the  phrenic 
at  the  base  of  the  neck,  in  the  rabbit. 
Observations, 
a.    Tactile  observation  of  the  diaphragm. 

(1)   In  what    condition  is  the  diaphragm  during  inspi- 
ration ?      Expiration  ? 


134 


LABORATORY  GUIDE  IN  PHYSIOLOGY 


(2)  In  what  position  is  the  diaphragm  during  these 
two  phases  of  respiration  ? 

(3)  What  parts  of  the  diaphragm  make  the  greatest 
change  of  position    during  inspiration  ? 

(4)  What  causes  the  diaphragm  to  arch  anteriorly 
during  normal  expiration?  Are  the  conditions 
changed  during  the  present  observations? 


Fig.  22. 


(5)  Are   the  diaphragmatic  movements  synchronous 
with  the  costal  movements? 

b.    The  normal  phreno gram. 

(6)  Take    a    phrenogram.       What     may    be     learned 
from  it? 

(7)  Without  varying  the   adjustment   of  the   phreno- 
graph   bulb,  take  a   tracing   while  repeatedly  inter- 


RESPIRATION.  135 

rupting    the    respiration    by    holding     the     nostrils 
What  does  the   phrenogram    show?     What    is    the 
interpretation? 

What  effect    upon  intra  thoracic   pressure    would 
the  holding  of  the  nostrils  have? 
c.    The  phrenic  nerve  and  its  junction. 

(8)  Describe  minutely  the  relations  of  the  nervus 
phrenicus  in  the  neck. 

(9)  Cut  the  nerve  while  tracing  a  phrenogram  from 
the  left  side  of  the  diaphragm.      Note  the  result. 

(10)  Take  a  phrenogram  from  the  right  side  of  the 
diaphragm.  Does  it  differ  essentially  from  the 
normal? 

(11)  While  taking  a  left  phrenogram  stimulate  the 
distal  end  of  the  left  phrenic  nerve.  Interpret  the 
result. 

(12)  While  taking  a  right  phrenogram  stimulate  the 
distal  end  of  the  left  phrenic  nerve.  Interpret  the 
result. 

(13)  Dissect  out  and  cut  the  right  phrenic  nerve. 
Does  the  diaphragm  cease  to  move?  If  it  moves,  is 
its  movement  active  or  passive?  Account  for  the 
phenomena. 

Kill  the  animal  with  chloroform. 


XXX.   Respiratory  pressure. 

/.  Appliances. — Operating  case;  clippers;  rabbit  board; 
ether;  ether  cone;  absorbent  cotton;  rabbit  stethograph; 
kymograph;  a  small  mercury  manometer,  to  the  piox- 
imal  limb  of  which  is  attached  a  thick  walled  rubber 
tube,  a  piece  of  glass  tubing  for  a  mouthpiece;  a  screw 
clamp;  chronograph;  two  recording  tambours;  rabbit. 

2.  Preparation. — Fix  and  anaesthetize  the  rabbit,  and  clip 
the  ventral  surface  of  the  neck.  Join  up  the  manometer 
as  shown  in  Fig.  23. 

j.  Operation. —  Make  a  longitudinal  incision  over  the 
trachea.  Carefully  pass  a  strong  linen  ligature  under 
the  trachea.  Make  a  median  ventral  slit  in  the  trachea 
anterior  to  the  ligature.  Pass  through  the  slit  the  limb 
of  the  Y-tube  marked  1.      (Fig.  23.)      Ligate. 

4.    Observations. 

a.   Respiratory  pressure.      The  pneumatogram. 

(1)  After  the  ligature  is  tied  how  does  the  rabbit 
breathe?  Are  the  thoracic  and  abdominal  move- 
ments of  respiration  accompanied  by  other  respira- 
tory movements? 

(2)  With  tube  n  (Fig.  23)  open  is  there  any  variation 
of  the  mercury  during  respiration? 

(3)  With  a  screw  clamp  slowly  close  tube  n.  As 
the  resistance  to  the  flow  of  air  increases  what 
change  is  noted  in  the  manometer? 

(4)  Quickly  clamp  tube  n  at  end  of  expiration  and 
carefully  note  the  manometer  reading.  Is  it  posi- 
tive or  negative? 

136 


RESPIRA  TION. 


137 


(5)  Clamp  tube  n  at  the  end  of  inspiration.  Is  the 
pressure  positive  or  negative? 

(6)  You  have  been  determining  certain  facts  regard- 
ing respiratory  pressure.  Are  the  causes  of  the 
changes  of  respiratory  pressure  the  same  as  the 
causes  of  the  changes  of  intra-thoracic  pressure  ? 

(7)  In  what  way  does  respiratory  pressure  differ  from 
intra- thoracic  pressure? 

(8)  Disjoin  the  manometer  and  join  its  tube  to  a  re- 
cording tambour  and  trace  a  pneumatogram,  with 
stethogram  and  chronogram. 

(9)  Compare  the  pneumstogram  with  the  tracing  of 
intra-thoracic  pressure.     Account  for  all  differences. 


U 


j  Centimrle 
Scale 


Fig.  23. 


(d)   Stimulation  of  the  pulmonary  vagus. 

(10)  Count  the  pulse.  Adjust  the  stethograph,  re- 
place the  manometer,  and  during  the  tracing  of  a 
stethogram  place  the  mouth  over  the  glass  mouth- 
piece; quickly  blow  into  the  tube  (n)  until  the 
manometer  indicates  two  centimeters  of  intra 
pulmonary  pressure;  clamp,  count  the  pulse.  After 
a  few  seconds  release  the  clamp  and  let  the  rabbit 
breathe  normally  for  a  few  minutes. 

Repeat  the  experiment.  Vary  by  producing  in  turn 
3  cm.,  then  4  cm.  and  finally  6  cm.  of  intra-pul- 
monary  pressure.  Fix  the  stethogram  and  com- 
pare. 


138  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(11)  Compare  your  results  with  those  obtained  from 
other  rabbits.  What  are  the  essential  features  of 
the   modified  stethogram  ?     Formulate  conclusions. 

(12)  What    effect     has    a    sudden    increase    of   intra 
pulmonary   pressure   upon   the    rate  of    the   heart's 
action. 

(13)  What  nerve  is  distributed  to  both  lungs  and 
heart?  Admitting  that  it  is  possible  for  the  ob- 
served effects  to  be  produced  through  the  agency 
of  the  nerves  just  named,  state  how  this  action  may 
be  accomplished. 

(14)  Could  the  effects  be  produced  in  any  other  way 
than  in  that  which  you  have  given  ? 

(15)  Is  the  demonstration  unassailable;  if  not,  what 
experiments  would  lead  to  results  conclusive  for  or 
against  the  theory? 

(16)  Is  the  minimum  intra-pulmonary  pressure, 
which  typically  modified  the  stethogram,  greater  or 
less  than  the  respiratory  pressure  of  forced  ex- 
piration ? 

(17)  What  effect  upon  intra  thoracic  pressure  would 
the  induction  of  high  intra-pulmonary  pressure 
have  ? 

(18)  What  effect  upon  blood  flow  would  high  intra- 
pulmonary  pressure  accompanied  by  repeated  acts 
of  forced  expiration  have?  What  incident  effect 
upon  the  rate  of  heart  beat? 

(19)  Dispatch  the  rabbit  with  chloroform  after  first 
arranging  the  apparatus  for  a  pneumatogram. 
While  holding  the  mouthpiece  over  or  in  a  chloro- 
form bottle  or  sponge,  take  a  characteristic  pneu- 
matogram of  chloroform  poisoning. 

c.    The  elasticity  of  the  rabbit's  lungs. 

(20)  After  the   death   of  the  rabbit   open   the  thorax 


RESPIRA  TION.  1 39 

freely,  taking  care  not  to  wound  the  visceral  pleura. 
The  lungs  will  collapse.     Why? 

(21)  Replace  the  manometer,  gently  blow  into  the 
mouthpiece  until  the  lungs  have  been  inflated 
to  their  normal  size.  Measure  carefully  the  rise  of 
mercury  in  the  distal  column. 

What  degree  of  positive  respiratory  pressure  will 
the  elasticity  of  the  lungs  alone  cause. 

(22)  What  is  the  significance  of  the  elasticity  of  the 
lungs  in  respiration? 

The  cardio-pneumatogram. — Remove   the  tube  n  from 
the  Y  tube,  join  it  to  a  recording  tambour. 

(23)  Let  a  member  of  the  division  sit  in  perfect 
repose,  and  while  the  drum  of  the  kymograph 
rotates  very  slowly,  hold  the  mouthpiece  between 
the  lips.  Hold  the  nose  and  suspend  all  respiratory 
movements  for  a  period.  Let  some  member  of  the 
division  count  the  pulse  of  the  experimenter. 

Trace  the  cardio-pneumatogram. 

(24)  Is  there  a  relation  between  the  rhythm  of  the 
pulse  and  the  waves  of  the  tracing  ?  If  so,  account 
for  this  relation. 

(25)  Account  for  the  essential  features  of  the  cardio- 
pneumatogram. 


XXXI.     Demonstration:     Quantitative   determination    of 

the  CO.,  and  H20  eliminated  from  an  animal 

in  a  given  time. 

1.  Appliances. — A  four-ounce  Woulff  bottle  with  three 
necks,  and  with  delivery  tubes  and  stopper  ground  in 
the  necks  [Fig.  24  a],  three  five-inch  calcium  chloride 
tubes,  with  side  tubes  and  perforated  glass  stoppers, 
opening  and    closing  the  flow  of    gas  [Fig.    24,  c,  e,  f]  ; 


CaCU  a^a,  UCh         CaCU         ^-^ 


Fig   24 

Fig.  24.      Apparatus  for  quantitative  determination  of    the  carbon 

dioxide  gas  and  water  eliminated  from  an  animal  in 

a  given  time. 

Geissler's  potash  bulbs  with  CaCl2  tube  ground  on  (g); 
two  small  flasks  (b,  h)  with  rubber  stoppers,  double-bored, 
with  delivery  tubes  fitted  as  shown  in  the  figure;  a  one 
or  two  liter  bottle  with  very  wide  mouth  to  use  as  an  an- 

140 


RES  FIR  A  TION.  141 

imal  cage,  fitted  with  delivery  tubes,  and  with  a  cork 
impregnated  with  paraffin;  siphon  apparatus,  as  figured, 
consisting  of  two  8  liter  bottles  with  paraffined  corks 
and  tubes;  analytical  balances;  laboratory  balances 
(correct  to  0.01  gm.);  drying  oven;  chemicals,  KOH, 
Ba(OH)2,  CaCh;  any  small  animal  whose  weight  in 
grammes  does  not  exceed  \  the  volume  of  the  animal 
cage  expressed  in  cubic  centimeters. 
2.  Preparation. 

(1)  Fill  the  calcium  chloride  tubes;  put  them  into  the 
drying  oven,  where  they  are  to  be  kept  at  a  tempera- 
ture of  100°  to  120°  C.  for  several  hours;  cool  in  a  des- 
iccator and  weigh  upon  the  analytical  balances  the 
tubes  e  and  f,  recording  the  weight  in  milligrammes. 

(2)  Fill  the  Woulff  bottle  and  the  Geissler's  bulbs  with 
a  strong  solution  (50%  or  more)  of  KOH.  Fix  into 
position  upon  the  Geissler  bulb,  its  filled  and  desic 
cated  CaCL  attachment,  and  fit  to  each  end  a  rubber 
juncture;  clamp  with  strong  serre-fineforceps  and  weigh 
upon  the  analytical  balances. 

(3)  Fill  the  flasks  b  and  h  with  a  strong  solution  of 
Ba(OH)3.  These  flasks  serve  simply  to  show 
whether  or  not  the  CO.,  gas  has  all  been  absorbed  by 
the  KOH  through  which  it  has  just  passed. 

(4)  Pieces  e,  f  and  g  should  be  fixed  to  a  light  wooden 
rack,  by  which  they  may  be  moved;  if  this  is  not  con- 
venient clamp  them  to  supports. 

(5)  Join  up  apparatus  a,  b  and  c. 

(6)  Fill  siphon  apparatus. 

(7)  Weigh  the  animal  cage. 
J.     Operation. 

(1)  Put  the  animal  into  the  jar;  fix  the  cover  so  that  it 
will  not  leak  air. 

(2)  Join    animal    cage    with    c  and   with    siphon  appa- 


142  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

ratus.  Start  the  siphon  and  note  the  rate  of  flow 
per  minute.  The  level  of  the  water  in  the  lower  hot 
tie  should  be  probably  1  meter  below  that  in  the  upper 
bottle.  Notice  whether  the  animal  seems  to  be  respir- 
ing normally;  if  so,  it  may  be  taken  for  granted,  after 
ten  minutes,  that  the  ventilation  is  sufficient.  If  it 
seems  insufficient  one  has  only  to  increase  the  differ- 
ence of  level  in  the  two  siphon  bottles. 

(3)  Disjoin  the  animal  cage  and  weigh  the  cage  with 
the  contained  animal  upon  the  laboratory  bal- 
ances. Note  the  time;  join  the  animal  cage  in  circuit 
again,  attaching  it  to  e,  and  attaching  z  to  h.  Start 
the  siphon.  The  greater  resistance  to  be  overcome 
will  necessitate  a  greater  difference  in  the  level  of  the 
two  bottles  in  order  to  ventilate  at  the  same  rate  as 
before.  To  test  joints  put  the  finger  over  the  distal 
tube  of  the  Woulff  bottle  (a);  if  the  joints  are  all  right 
the  siphon  stream  will  stop  after  a  few  moments.  When 
the  water  in  the  upper  bottle  is  lowered  nearly  to  the 
end  of  the  siphon,  clamp  the  tube  joining  h  to  i,  set 
the  empty  bottle  upon  the  floor  and  the  full  bottle 
upon  the  higher  level,  join  the  tube  on  at  k  and  un- 
clamp.  This  whole  change  need  only  occupy  a  few 
seconds.  In  the  meantime  C02  has  been  collecting, 
but  it  has  not  been  lost. 

(4)  It  is  evident  that  in  the  afferent  apparatus  (a,  b  and 
c)  one  has  a  means  of  robbing  the  air  of  COs  and 
HoO,  thus  furnishing  the  animal  with  pure,  dry  air. 
It  is  further  evident  that  in  the  efferent  apparatus  one 
has  a  means  of  collecting  absolutely  all  of  the  C02 
and  H30  given  off  by  the  animal  during  the  experi- 
ment. Further  the  weights  before  and  after  will  show 
just  how  much  of  these  excreta  have  been  passed  into 
the  collecting  apparatus. 


RESPIRATION.  143 

(5)  Note  the  time  (one  hour  or  more);  clamp  siphon 
tube;  turn  the  stoppers  of  e  and  f,  clamp  x  and  y; 
disjoin  d  and  weigh  it. 

(6)  Weigh  e;  weigh  f;   weigh  g. 
Observations. 

1)   How  much  has  the  animal  lost  in  weight  during  the 
period  of  observation? 

(2)  How  much  water  left  the  animal  cage  during  the 
period  of  observation? 

(3)  What  was  the  source  of  this  water? 

(4)  Did  the  animal  micturate  or  defecate  during  the 
time  of  the  experiment?  If  so,  is  this  to  be  looked 
upon  as  a  source  of  error  in  the  experiment?  Would 
such  an  occurrence  tend  to  increase  or  to  decrease  the 
amount  of  water  caught  in  the  CaCl2  tubes  e  and  f? 
Would  it  cause  a  discrepancy  between  the  loss  in 
weight  of  the  animal,  as  determined,  and  the  com- 
bined weight  of  collected  H.,0  and  C02? 

(5)  How  much  C02  left  the  animal  cage  during  the 
observation  ? 

(6)  What  is  the  total  amount  of  H20  and  COo  collected? 

(7)  Does  the  amount  of  these  excreta  collected  equal 
the  loss  in  weight  in  the  animal?  What  should  the 
relation  of  these  two  quantities  be?     Explain  in  full. 

(8)  What  is  the  respiratory  quotient? 

(9)  Formulate  several  problems  which  may  be  solved 
with  this  method? 


XXXII.   Respiration   under   abnormal  conditions. 

/.  Appliances. — Three  small  animals,  e.  g.,  mice,  rats, 
guinea  pigs  or  squirrels.  Three  wide  mouthed  bottles 
or  jars  which  may  be  sealed;  scales  or  large  balances; 
C02  generator;  water  bath;  operating  case;  dissecting 
boards. 

2.  Preparation. — Determine  the  weight  of  each  animal. 
Choose  a  receptacle  whose  cubic  contents  is  about  two  to 
three  times  as  many  cubic  centimentersas  the  weight  of 
animal  "a"  in  grams.  Choose  second  and  third  recep- 
tacles whose  contents  represent  about  12  to  15  c.  c.  to 
one  gram  of  animils   "b"  and  "c,"  respectively. 

j.    Operation. 

I.  Preliminary. 

a.  Put  animal  "a"  into  the  small  jar  "a";  count  res- 
pirations; close  the  jar. 

b.  Put  animal  "b"  into  jar  "b."  Before  closing  count 
respirations;  close  airtight. 

c.  Fill  jar  "c"  one-third  full  of  water  and  displace  the 
water  with  C02.  Put  animal  "c"  into  the  jar,  tak- 
ing care  to  allow  as  little  loss  of  C02  as  possible; 
close;  count  respirations. 

II.  Post-mortem  examination. 

After  an  animal  dies  fix  it  to  the  dissecting  board  and 

open  the  abdominal  and  thoracic  cavities;  take  great 

care  not  to  cut  a  large  blood  vessel;  pin  the  flaps  out 

so  that  all  of  the  organs  will  be  exposed  and  in  place. 

4.    Obsertmtions. 

a.  Respiration  in  small  closed  space. 

(1)  Make  careful    record   of    number    of    respirations 

144 


RES  PI R  A  TION.  1 45 

and  general  condition  of  animal  "a"  in  the  normal 
state,  and  at  the  end  of  every  five  minutes  after  the 
closure  of  the  jar. 

What  changes  in   rate  or    depth     of    respiration 
have  been  noted? 

(2)  Note  all  abnormal  signs  and  symptoms. 

(3)  On  post-mortem  examination  record  the  condi- 
tion of  heart,  large  blood  vessels,  lungs,  liver,  kid- 
neys and  the  general  appearance  of  the  tissues. 

(4)  Compare  the  conditions  with  those  found  in  a 
normal  animal,  prepared  by  the  demonstrator. 

Respiration  in  a  larger  closed  space. 

(5)  Note  all  symptoms  of  animal  "  b  "  every  five  min- 
utes after  confinement  in  the  jar. 

(6)  Make  a  post-mortem  examination;  record  in  de- 
tail the  condition  of  the  organs  as  in  the  case  of 
animal  "  a." 

(7)  Compare  animal  "  b  "  with  the  normal  animal. 

(8)  Compare  animal  "  b  "  with  animal  "  a." 
Respiration  in  an  atmosphere  of  one- third  C02 

(9)  Note  all  symptoms  at  intervals  of  five  minutes. 

(10)  Compare  these  observations  with  corresponding 
ones  from  animal  "  a  "  and  animal  "  b."  What  are 
your  conclusions  ? 

(11)  Make  a  post-mortem  examination;  make  a  record 
as  before. 

(12)  Compare  appearances  in  animal  "c"  with  those 
in  the  normal  animal,  with  those  of  animal  "a;" 
with  those  of  animal  "b." 

(13)  Make  a  generalized  statement  of  the  facts  dis- 
covered in  the  experiments. 

(14)  What  is  the  cause  of  death  when  an  animal  is 
inclosed  in  a  small  space? 


146  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(In)   What  is  the  cause  of  death  when   an   animal  is 

inclosed  in  a  large  space  ? 
(16)   Have  the  relations  which  you  have  discovered 

any  bearing  upon  the  future  development  of  animal 

life  upon  the  earth  ? 


XXXHI.    Respiration  in  abnormal  media. 

i.  Appliances. — Three  small  animals;  three  jars  or  wide- 
mouthed  bottles;  hydrogen  generator;  nitrogen  genera- 
tor; water  bath;  potassium  nitrite;  ammonium  chloride; 
operating  case;  dissecting  boards. 

2.  Preparation. — Dissolve  66  grammes  of  ammonium  chlor- 
ide in  500  cubic  centimeters  of  water.  Dissolve  100 
grammes  of  potassium  nitrite  in  500  cubic  centimeters  of 
water.  Prepare  a  nitrogen  generator  as  shown  in  the 
figure,  using  a  liter  flask.      (Fig.  25.) 

3.  Operation. 

a.  Pour  the  two  solutions  into  the  generator;  adjust  con- 
ducting tube;  heat  the  mixture  in  the  generator;  in  a 
few  minutes  nitrogen  gas  will  be  given  off  from  the 
mixture  as  the  result  of  the  following  reaction: 

NH4C1+KN0,=2H,0+KCI  +  N2. 
If  the  jars  used  by  the  different  divisions  are  not  too 
large  the  above  suggested  quantities  of  the  solutions 
will  probably  supply  enough  gas  for  several  divisions. 
Put  an  animal  into  the  jar  of  nitrogen  and  close  the 
jar. 

b.  Fill  a  jar  full  of  water,  displace  it  with  hydrogen 
gas.      Put  an  animal  into  the  jar  and  close  it. 

c.  Put  an  animal  into  a  third  jar,  confining  it  with  a 
cloth  or  a  sheet  of  rubber.  Join  a  rubber  tube  to  an 
illuminating  gas  jet,  introduce  the  end  of  the  tube  in- 
to the  mouth  of  the  jar;  turn  the  gas  on  for  an  instant 
only.  After  five  minutes  allow  another  momentary 
puff  of  illuminating  gas  to  enter  the  jar. 

147 


148 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Observations. 

a.  Respiration  in  an  atmosphere  of  nitrogen. 

(1)  Note  all  symptoms. 

(2)  How  do   these  compare   with  those  of   death  by 
oxygen  starvation  ? 

(3)  Record  post-mortem  appearances. 

(4)  Compare  with  previous  cases. 

b.  Respiration  in  an  atmosphere  of  hydrogen. 

(5)  Note    carefully  every  abnormal    appearance  and 
symptom. 

(6)  Make  a  record  of  the   post-mortem   appearances. 


Fig.  25. 


Fig.  2").      Nitrogen  generator. 


(7)  Compare   these  with   the  appearances  after  death 
by  oxygen  starvation;  by  C03  narcosis. 

c.  Respiration  in    an    atmosphere  of  one- third  illuminating 
gas  (CO+). 

(8)  Record  all  symptoms. 

(9)  Record  post-mortem  appearances. 


RESPIRA  I  ION.  149 

(10)  How  does  death  in  an  atmosphere  of  CO  com- 
pare, as  to  symptoms,  with  death  in  an  atmosphere 
of  nitrogen  ? 

(11)  Compare  it  in  turn  with  other  forms  of  death  as 
induced  in  this  and  the  previous  chapter. 

(12)  Compare  the  post-mortem  appearances  in  this 
case  with  those  in  preceding  cases. 


E.     DIGESTION  AND  ABSORPTION. 


As  intimated  in  the  introduction  it  is  taken  for  granted 
that  by  the  time  a  medical  school  has  found  the  conditions 
propitious  for  the  establishment  of  a  laboratory  of  experi- 
mental physiology,  the  whole  province  of  chemical  physiol- 
ogy will  have  been  occupied  by  the  department  of 
chemistry  as  a  legitimate  growth  of  that  department. 

The  American  laboratory  of  experimental  physiology 
will  present,  almost  exclusively,  the  physical  problems  of 
physiology.  But  even  where  such  are  the  conditions  it 
may  seem  advisable  to  introduce  into  a  course  of  lectures 
or  recitations  on  the  physiology  of  digestion  a  series  of 
demonstrations. 

The  following  exercises  in  the  chemistry  of  digestion 
and  the  physics  of  absorption  may  be  given  either  as  dem- 
onstrations or  as  laboratory  exercises. 

This  chapter  is  not  intended  as  a  substitute  for  any  of 
the  excellent  treatises  now  used  in  medical  schools,  but 
rather  as  a  supplement  to  them. 

It  will  be  taken  for  granted  that  the  student  has  had  at 
least  one  year  of  chemistry  before  he  enters  upon  this 
course. 

To  give  the  course  which  is  outlined  one  will  need  the 
following  appliances,  apparatus  and  reagents. 

160 


DIGESTION  AND  ABSORPTION.  151 

Appliances : 

a.  Glass  ware  utensils,  6-v.  ; 

10  evaporating  dishes,  assorted  sizes  ; 
10  filters  assorted  sizes — 5  cm.  to  20  cm; 
100  test  tubes  15  cm  ; 
10  beakers  30  c.c.  ; 
10  beakers  assorted — 50  c.c.  to  2  L.  ; 
10  50  c.c.  graduated  cylinders; 

4  graduated    cylinders — 100    c.c,    200   c.c,  500  c.c, 
1000  c.c. 

3  wedgewood    mortars  (2^,  4  and  7  in.  in  diameter)  ; 
Filter  paper; 
Labels  ; 
Pig  bladders  ; 
Thread  ; 
Rubber  tubing ; 
Glass  stirring  rods ; 

b.  Apparatus. 

3  Bunsen  burners — with  rubber  tubing; 
Filter  stand  ; 

2  supports  with  rings  and  gauze; 
8  dialyzers 

1  incubator; 
Drying  oven  ; 
Meat  hasher 
Desiccator ; 

3  Water  baths  ; 

Platinum  dish — 15  c.c.  to  100  c.c. 

c.  Reagents. 
Diluted  iodine  ; 
Fehling's  solution  ; 

Sodium  hydrate  and  potassium  hydrate; 
Copper  sulphate; 
Distilled  water; 


152  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

Neutral  litmus  ; 
Concentrated  nitric  acid  ; 
Strong  ammonia  ; 
Acetic  acid; 
Osmic  acid  1  %  ; 
Pure  standard  pepsin  ; 

Muriatic  acid  C.  P.   (  Sp.  gr.  1.16  =  31.9  %  abs.  HC1  ;) 
Absolute  alcohol ; 
Ether ; 
Chloroform ; 
Calcium  chloride  ; 
25  %  solution  NaOH  ; 
25  %  solution  KOH  ; 
%  saturated  solution  Na2C03  ; 

Nonmedicated  absorbent  cotton  for  rapid  filtering  of 
mucilaginous  or  albuminous  liquids. 


XXXIV.  The  carbohydrates. 

/.  Materials. — Potato  starch ;  dextrin;    dextrose;    maltose; 

lactose;  saccharose;  celiulose  represented  by  absorbent 

cotton  and  ashless  filter  paper. 
2.   Preparation. 

(1)  To  prepare  Fehling 's  solution: 

a.  Into  a  half-liter,  glass-stoppered  bottle  put  34.64 
gm.  CuS04  c.p.,  and  enough  H20  dist.  to  make 
500  c.  c.      Label  the  solution:   Fehling1  s  solution  (a). 

b.  Into  a  similar  receptacle  put  173  gms.  of  potassic- 
sodic  tartrate  —  KNaC4H406+4H20  [Rochelle 
salt]  and  50  gm.  of  NaOH,  weighed  in  sticks;  add 
enough  water  to  make  500  c  c.  Label:  Fehling 's 
solution  (b~).  For  use  mix  these  two  solutions  in 
equal  parts.  A  convenient  quantity  for  the  follow- 
ing experiments  is  50  c,  c.  of  each  in  100  c.  c.  bottle. 

(2)  Prepare  a  starch  paste  by  rubbing  1  gm.  of  starch  to  a 
creamy  consistence  with  water,  add  100  c.  c.  of  distilled 
water  and  boil. 

(3)  Prepare  a  dilute  solution  of  iodine  by  direct  solu- 
tion in  water  or  by  diluting  an  alcoholic  solution. 

J.  Fxperiments  and  Observations. 

(1)  Put  a  little  dry  starch  into  an  evaporating  dish;  add 
some  dilute  iodine.  The  starch  turns  blue.  Pour  a 
few  drops  of  starch  paste  into  a  test  tube;  add  a  few 
drops  of  iodine.  Iodine  may  be  used  to  detect  the 
presence  of  raw  or  of  cooked  starch. 

(2)  Put  some  raw  starch  into  a  test  tube  or  beaker;  add 
water;  stir.     The  starch  does  not   seem    to  be  at  all 

153 


154  LABORATORY  GUIDE  JAT  PHYSIOLOGY. 

soluble  in  water.  Stir  or  shake  the  mixture  to  bring 
the  starch  into  suspension  in  the  water;  pour  upon  a 
filter.  A  clear  filtrate  passes  readily  through.  Test 
the  filtrate  for  starch;  result,  negative;  pour  a  few 
drops  of  iodine  upon  the  filter,  starch  present.  Con- 
clusions: 

(<7)   Potato  starch  is  insoluble  in  cold  water. 

(b)  The  granules  of  potato  starch  will  not  pass 
through  common  filter  paper. 

(3)  Dilute  a  few  cubic  centimeters  of  starch  paste;  pour 
it  upon  a  filter;  to  the  filtrate  add  iodine.  The  blue 
color  indicates  that  in  the  cooking  of  starch  the  grains 
are  broken  up  into  particles  sufficiently  small  to  readily 
pass  through  the  meshes  of  common  filter  paper. 

(4)  In  order  to  determine  whether  dilute  starch  paste 
will  in  response  to  the  laws  of  osmosis  pass  through 
an  animal  membrane,  fill  a  dialyzer  with  dilute  starch 
paste.      Set  aside  to  be  tested  one  or  two  days  later. 

(5)  Put  a  bit  of  absorbent  cotton  into  a  beaker  or  test 
tube;  add  water,  boil;  add  iodine.  Cellulose,  as  repre- 
sented by  cotton  fibers,  is  insoluble  in  water  and  does 
not  respond  to  the  iodine  test. 

(6)  Put  a  few  bits  of  ash-free  filter  paper  into  a  test 
tube;  add  water;  boil;  add  iodine.  Cellulose,  as  repre- 
sented by  the  fibers  of  ash  free  filter  paper,  is  insol- 
uble in  water  and  responds  to  the  iodine  test.  One 
must  remember  in  this  connection  that  in  the  prepa- 
ration of  ash-free  filter  paper  mineral  acids  are  used 
to  dissolve  out  the  salts;  and  mineral  acids,  especially 
sulphuric  acid,  so  modify  cellulose  that  it  responds  to 
the  iodine  test  with  a  blue  color. 

(7)  Add  water  to  dextrin  in  a  beaker;  stir  with  a  rod. 
Dextrin  is  readily  soluble  in  cold  water.  To  a  small 
portion  add   iodine.     The  solution  will   probably  as- 


DIGESTION  AND  ABSORPTION.  155 

sume  a  wine  color;   the  typical  reaction  of  erythro  dex- 
trin. 

(8)  Fill  a  dialyzer  with  diluted  dextrin  solution  and 
leave  for  subsequent  examination. 

(9)  Add  water  to  dextrose;  it  is  readily  soluble.  Add 
iodine  to  a  portion  of   the  solution;  result,  negative. 

(10)  Fehling's  test  for  a  reducing  sugar:  To  a  few  drops 
of  the  solution  add  several  cubic  centimeters  of  Feh- 
ling's  solution  and  boil.  A  yellowish  precipitate  of 
cuprous  oxide  (CuO)  appears.  If  the  boiling  is  con- 
tinued the  color  changes  to  a  brick  dust  red. 

(11)  To  a  solution  of  maltose,  add  Fehling's  solution 
and  boil;  the  copper  solution  is  reduced  and  CuO  is  pre- 
cipitated. 

(12)  To  a  solutionof  lactose,  add  Fehling's  solution  and 
boil]  reduction  takes  place. 

(13)  Subject  a  solution  of  saccharose  to  the  Fehling 
test.     No  reduction  occurs. 

(14)  Tromer's  test  for  a  reducing  sugar:  To  any  liquid 
suspected  of  containing  a  reducing  sugar,  add  a  few 
drops  of  very  dilute  CuS04  solution;  to  this  mixture, 
add  an  excess  of  NaOH  (or  KOH);  boil;  if  the  sus- 
pected liquid  contain  a  reducing  sugar,  the  CuS04  will 
be  reduced  with  precipitation  of  CuO.  Subject  all 
of  the  solutions  of  sugar  in  turn  to  the  Tromer  test. 
Note  that  the  appearance  is  practically  the  same  as 
with  the  Fehling  test.  Any  differences  are  due,  not  to 
a  difference  in  the  essential  reaction  but  to  a  difference 
in  the  proportions  of  the  two  reagents.  The  Fehling 
test  is  more  satisfactory. 

(15)  Fill  a  dialyzer  with  a  dilute  solution  of  dextrose  for 
subsequent  examination. 


156  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(16)  Fill  a  dialyzer  with  a  dilute    solution  of  maltose  or 
lactose  for  subsequent  examination. 

(17)  Fill  a  dialyzer  with  a  dilute  solution  of  saccharose 
for  subsequent  examination. 

Questions  and  Problems. 

(a)  How  may  carbohydrates  be  classified  ?  [Make  three 
classes.] 

(b)  Which  class  has  the  lowest  grade  of  hydration? 

(c)  How  many  of  this  class   are  soluble  in  cold  water? 

(d)  How  many  are  diffusible  ? 

(e)  Which  class    has    the  highest  grade  of  hydration? 

(f)  Are  all  of  those  which  belong  to  the  third  class 
soluble  in  water  ? 

(g)  Are  they  all  diffusible  ? 

(h)   How  may  dextrin  be  classified  ? 

(j)  How  many  of  the  carbohydrates  reduce  CuS04  in 
presence  of  an  excess  of  NaOH  or  KOH  ? 

(k)   How  many  of  the  carbohydrates  are  diffusible  ? 

(1)  How  may  one  determine  whether  or  not  cane  sugar 
passed  ihrough  the  animal  membrane  ? 


XXXV.     Salivary  digestion. 

/.   Materials. — Bread;    fibrin;     pig-fat;     olive    oil;     starch 

paste;  cane  sugar. 
2.    Preparation. 

Remove  the  parotid  and  submaxillary  glands  of  several 
rabbits  or  rats,  hash  them;  rinse  quickly  with  water  to 
remove  blood;  cover  with  water.  After  a  few  hours 
(12-24)  filter  or  strain  off  the  opalescent  aqueous  ex- 
tract. It  should  contain  an  aqueous  solution  of  ptya- 
lin.      Label:     Salivary  Extract. 

(2)  Chew  a  piece  of  rubber  or  paraffin.  The  flow  of 
saliva  is  stimulated;  catch  the  secretion  in  a  beaker; 
dilute  and  filter.      Label:   Salivary  Secretion. 

(3)  Fibrin  for  use  in  experiments  on  digestion  may  be 
procured  in  any  quantity  at  a  slaughter  house.  Rid  it 
of  all  red  coloring  matter  and  of  accidental  contamina- 
tion by  repeatedly  soaking  and  washing  in  water.  The 
white,  elastic  shreds  of  fibrin  may  be  kept  indefinitely 
in  pure  glycerin.  For  use  one  needs  only  to  wash 
out  the  glycerin  thoroughly. 

j.    Experiments  and  Observations. 

(1)  Subject  saliva  {a)  and  (/>)  to  the  Fehling  test. 
It  will  be  found  that  neither  the  extract  nor  the  secre- 
tion will  reduce  the  CuS04. 

(2)  Subject  starch  paste  to  the  same  test.  The  result 
is  negative. 

(3)  Mix  equal  volumes  of  starch  paste  and  salivary 
extract  in  a  beaker.  Place  the  mixture  in  the  incu- 
bator, which  is  kept  at  a  temperature  of  35°  to  40°  C. 

157 


158  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

After  ten  or  fifteen  minutes  subject  the  mixture  to  a  test 
with  Fehling's  solution.  If  the  conditions  are  normal  a 
copious  precipitate  of  CuO  indicates  that  a  change  has 
been  wrought  in  the  mixture.  The  starch  has  been 
changed  to  a  reducing  sugar  by  the  ptyalin  of  the 
salivary  extract. 

(4)  Mix  equal  volumes  of  starch  paste  and  salivary 
secretion  in  a  beaker,  place  the  mixture  in  the  incu- 
bator for  ten  or  fifteen  minutes;  test  with  Fehling's 
solution.  The  presence  of  a  reducing  sugar  shows 
that  the  secretion  of  the  human  salivary  glands  has 
the  power  to  change  starch  to  sugar;  to  change  an  in- 
soluble, indiffusible  foodstuff  to  a  soluble,  diffusible 
one. 

(5)  Put  a  few  crumbs  of  bread  into  a  test  tube;  add 
dilute  iodine.  Starch  is  an  important  constituent  of 
bread. 

(6)  Put  a  few  crumbs  of  bread  into  a  beaker;  add 
salivary  extract;  place  in  the  incubator  twenty  minutes. 
Disintegration  of  the  pieces  and  a  marked  increase  of 
the  amount  of  reducing  sugar  indicates  the  digestive 
action  of  saliva  upon  bread. 

(7)  Put  a  bit  of  fibrin  into  salivary  extract;  place  in 
the  incubator.  An  hour  or  a  day  will  show  no  appar- 
ent change  in  the  fibrin.  Had  one  used  any  other 
proteid  the  result  would  have  been  the  same.  We  are 
justified  in  the  conclusion  that  saliva  contains  no 
ferment  capable  of  changing  proteids. 

(8)  Put  a  bit  of  fat  or  a  drop  of  oil  into  a  few  cubic  cen- 
timeters of  salivary  extract,  shake  vigorously;  place  in 
incubator.  After  an  hour  or  day  one  sees  no  change  in 
the  fat  or  oil,  and  is  justified  in  the  conclusion  that 
saliva  contains  no  ferment  which  acts  upon  fats. 

(9)  To  a  small  amount  of  raw  starch    add   salivary  ex- 


DIGESTION  AND  ABSORPTION.  159 

tract,  place  the  mixture  in  the  incubator;  shake  fre- 
quently; after  fifteen  minutes  test  for  reducing  sugar. 
There  will  probably  be  a  relatively  small  amount  of 
reducing  sugar.  If  one  watches  the  progress  of  the 
digestion  for  several  hours  he  will  be  convinced  that 
the  cooking  of  starch  very  greatly  facilitates  its  diges- 
tion by  saliva. 

(10)  Boil  a  few  cubic  centimeters  of  saliva;  add  starch 
paste;  place  in  the  incubator  for  ten  minutes;  test  for 
reducing  sugar.      What  is  the  verdict? 

(11)  Test  the  salivary  secretion  with  neutral  litmus. 
Determine  whether  its  faint,  alkaline  reaction  is  essen- 
tial to  its  action  as  a  digestive  fluid. 

(a)  To  one  portion  of  saliva  add  an  equal  volume 
of  0.3%  hydrochloric  acid  and  the  same  amount 
of  starch  paste.  The  mixture  represents  0.1% 
hydrochloric  acid.  Place  the  mixture  in  the 
incubator  for  fifteen  minutes;  test  with  Fehling's 
solution.     Verdict  ? 

(£)  Repeat  the  experiment  substituting,  for  the 
hydrochloric  acid,  lactic  acid  of  the  same  strength; 
place  in  the  incubator  for  fifteen  minutes;  test  with 
Fehling's  solution. 

What  is  the  conclusion  ? 

(12)  To  determine  the  course  of  salivary  digestion.  Mix 
50  c.  c.  of  salivary  extract  with  an  equal  amount  of 
starch  paste.  Test  a  portion  with  iodine  at  once. 
Test  another  portion  at  once  with  Fehling's  solution. 
Keep  the  beaker  in  a  water  bath  at  blood  tempera- 
ture. Test  a  portion  of  the  mixture  every  minute 
with  iodine  and  another  portion  every  minute  with 
Fehling's  solution. 

{a)  What  is  the  first  change  noted  in  the  digestion 
of  the  starch  ? 


160  LABOR  A  TOR  Y  GUIDE  IN  PH  YSIOLOG  Y. 

(6)  How  many  steps  may  be  made  out  with  the 
means  used  and  under  the  conditions  existing  in 
the  experiment  ? 

(<r)   In  what  order  do  the  changes  occur? 

(13)  Place  some  starch  paste  in  a  beaker  which  may  be 
floated  in  ice  water;  similarly  float  a  beaker  with 
saliva.  After  both  liquids  have  been  cooled  down  to 
near  the  temperature  of  the  surrounding  water,  mix 
them  in  one  of  the  beakers;  keep  the  mixture  at  the 
low  temperature  while  subjecting  portions  of  it  every 
two  minutes  to  the  tests  suggested  above. 

(a)  May  the  same  changes  be  made  out  in  this  ex- 
periment as  in  the  previous  one? 

(/>)   Are  the  changes  in  the  same  order? 

(c)  State  any  differences  in  salivary  digestion  at 
blood  temperature  and  at  the  low  temperature 
(0°C)  used  in  this  experiment. 

(14)  (a)  Sum  up  the  day's  work  in  a  series  of  conclu- 
sions. 

{/>)  What  is  the  chemical  formula  of  starch?  Of 
erythro-dextrin  ?     Of  maltose?     Of  dextrose? 

(c)  Write  a  chemical  reaction  or  a  series  of  reac- 
tions which  will  be  in  harmony  with  the  observa- 
tions and  show  as  nearly  as  possible  the  course  of 
salivary  digestion. 

{d)  What  change  has  the  ferment  wrought  in  the 
starch  molecule  to  render  the  resulting  carbohy- 
drate capable  of  diffusion  through  animal  mem- 
brane ? 


XXXV!.    The  proteids. 

/.  Materials. — An  egg;  fibrin;  gelatine;  myosin;  syntonin; 
acid  albumin;  commercial  peptone  (mixed  albumoses, 
proteoses  and  peptones);   Grubler's  pure  peptone. 

2.    Preparation. 

(a)    To  prepare  myosin: 

(1)  Take  one  pound  of  lean  meat,  grind  it  in  the  meat 
hasher;  soak  and  wash  repeatedly  until  the  tissue  is 
nearly  white  and  quite  free  from  haemoglobin. 

(2)  Put  the  washed  muscle  tissue  into  a  flask  with  an 
equal  bulk  of  a  20%  solution  of  ammonium  chloride; 
shake  from  time  to  time  for  24  hours. 

(3)  Strain  off  the  liquor  and  add  to  it  20  volumes  of  dis- 
tilled water.  Myosin  is  precipitated.  Wash  the  pre- 
cipitate. Redissolve  one  fourth  of  the  precipitate  in 
10%  NaCl,  and  label:    Saline  Solution  of  Myosin. 

b.  To  prepare  syntonin. — To  the  remaining  three-fourths 
of  the  washed  myosin  add  several  volumes  of  0.1%  hy- 
drochloric acid.  In  a  very  short  time  the  myosin  will 
be  dissolved  and  changed  to  syntonin. 

c.  To  prepare  dilute  egg  albumin. — Make  an  opening  in 
one  end  of  the  shell  of  an  egg;  drain  off  the  white  of  the 
egg,  catching  it  upon  a  coarse  linen  cloth — a  towel  serves 
the  purpose  well;  press  the  albumin  through  the  meshes 
of  the  linen  into  a  beaker;  add  400  or  500  cubic  centi- 
meters of  distilled  water;  transfer  the  mixture  to  a  1  L. 
cylinder  and  shake  vigorously;  after  a  short  time  filter 
through  pure  absorbent  cotton  or  strain  through  fine 
linen. 

161 


162  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

d.  To  prepare  acid  albumin. — To  100  c.c.  of  dilute  egg 
albumin  add  an  equal  quantity  of  0.2%  hydrochlo- 
ric acid;  place  the  mixture  in  the  incubator  for  two 
or  three  hours.  Though  the  change  begins  at  once  it 
will  probably  not  be  complete  before  the  time  suggested. 
If  one  wishes  to  isolate  the  acid  albumin  from  the  mix- 
ture he  has  only  to  carefully  neutralize  with  sodic  hy- 
droxide precipitating  the  acid  albumin,  and  to  wash  the 
precipitate  with  distilled  water.  For  the  purposes  for 
which  it  is  to  be  used  in  the  following  demonstration  it 
may  be  left  in  the  acid  solution  which  represents  0.1% 
HC1. 

Label:      Acid  Albumin  Solution  in  0.1%  HC1. 
e. — Make  an  aqueous  solution  of  the  commercial  "pep- 
tone," and  though  peptone  is  present  in  small  propor- 
tion, label  it:    Proteoses. 

f.  Make  an  aqueous  solution  of  a  few  grammes  of  Gru- 
bler's  pure  peptone,  and  label:  Peptone. 

g.  Dissolve  a  few  grammes  of  gelatin  in  distilled  water. 
h.    To  prepare  Millon's  reagent:    1st.    To  100  grammes  of 

pure  mercury  add  an  equal  weight  of  concentrated 
nitric  acid  c.  p.  The  reaction  proceeds  at  room 
temperature,  though  gentle  heat  may  be  applied  to 
complete  the  solution  of  the  mercury.  2d.  Cool  the 
mixture;  add  two  volumes  of  water;  after  12  hours 
decant  the  supernatant  liquid — Milton's  Reagent, 
j.  Experiments  and  Observations. 

(1)  Pour  into  test  tubes  a  few  cubic  centimeters  of 
each  of  the  following  proteid  solutions  and  subject 
each  in  turn  to  a  temperature  of  57°C,  then  to  a  tem- 
perature of  63°C,  and  finally  a  temperature  of  100°C, 
by  dipping  the  tubes  into  waterbaths  of  the  tempera- 
tures named: 

(a)  Dilute  egg  albumin. 


DIGESTION  AND  ABSORPTION.  163 

(&)  Saline  solution  of  myosin. 
(V)  Syntonin  in  acid  solution. 
(</)  Acid  albumin  in  acid  solution. 
(e)  Gelatin  in  aqueous  solution. 
(/)  Proteoses. 
(g)  Peptone. 

Record  the  results  in  a  table   and   formulate  con- 
clusions. 

(2)  Subject  the  same  series  of  proteids  to  the  cold  nitric 
acid  test  by  first  pouring  one  or  two  cubic  centimeters  of 
strong  nitric  acid  into  a  test  tube,  then  with  pipette  care- 
fully floating  the  proteid  liquid  upon  it.  In  the  case  ot 
dilute  egg  albumin  a  characteristic  white  ring  forms 
between  the  acid  and  the  albumin.  Note  in  each  case 
whether  or  not  a  typical  ring  is  formed. 

(a)   Dilute  egg  albumin. 

(£)  Saline  solution  of  myosin. 

(c)   Syntonin. 

(</)  Acid  albumin. 

(^)   Gelatin. 

(/)  Proteoses. 

(g)  Peptone. 

Tabulate  results  and  formulate  same  in  a  concise 
statement. 

(3)  The  Xanthoproteic  test. 

Use  the  tubes  and  materials  already  prepared  in  the 
cold  nitric  acid  test.  Shake  the  tubes  to  mix  the  acid 
with  the  proteid.  In  some  cases  a  coagulum  will  be 
formed  and  this  coagulum  turns  yellow  on  boding  if 
the  tube  is  held  in  a  Bunsen  flame.  After  the  coagu- 
ium  has  been  boiled  in  the  acid,  cool  under  the  hydrant 
or  in  a  pail  of  ice  water  and  add  strong  ammonia  to 
alkaline  reaction.  The  light  yellow  coagulum  which 
forms  in  the  case  of  egg  albumin  turns  to  an  orangecolor. 


164  LA  B  OR  A  TORY  G  UIDE  IN  PH  YSIOL  OGY. 

This  test  is  usually  given  as  a  universal  proteid  test. 
Tabulate  results  on  the  above  suggested  series  (a)-(g) 
noting  any  variations  of  the  reaction  in  the  different 
proteids.  Besides  variations  in  the  reaction  with  dif- 
ferent proteids  there  are  marked  variations  with  differ- 
ent strengths  of  solution  of  the  same  proteid. 

(4)  A  general  test  for  proteids  is  to  heat  a  proteid-con- 
taining  liquid  with  half  its  volume  of  Milloris  reagent. 
A  precipitate  appears  which  is  yellowish  at  first  but 
turns  red  under  the  influence  of  heat.  Test  each  of 
the  above  list  of  proteids  (a-g),  with  Millon's  reagent. 
Record  results. 

(5)  The  Biuret  test. 

To  a  suspected  liquid  add  an  excess  of  sodic  hydrate; 
shake  well  and  to  the  mixture  add  one  or  two  drops 
of  a  very  dilute  solution  of  cupric  sulphate.  A  violet 
color  appears  which  on  heating  becomes  deeper  in 
shade. 

A  most  convenient  reagent  for  this  reaction  is  a 
mixture  of  the  solutions  (a)  and  (b)  of  the  Fehling's 
test  not  in  equal  quantities  as  in  the  typical  Fehling's 
solution,  but  in  the  proportion  of  nine  parts  of  the 
sodic  hydroxide  solution  (b)  to  one  part  of  the  cupric 
sulphate  solution  (a)  and  add  an  equal  volume  of  dis- 
tilled water  to  the  mixture. 

Tabulate  results  on  the  proteid  series  (a)  to  (g). 

(6)  Subject  each  of  the  series  of  proteids  (a)  to  (g)  to 
each  of  the  following  reagents  tabulating  results: 

(I)  Picric  acid,  saturated  solution. 

(II)  Absolute  alcohol. 

(III)  Mercuric  chloride,  saturated  solution. 

(IV)  Tannic  acid,  saturated  solution. 

(V)  Silver  nitrate,  10%  solution. 

(VI)  Ammonium  sulphate,  saturated  solution. 


DIGESTION  AND  ABSORPTION  165 

On  which  of  the  proteid   solutions  would  one  get 

a  precipitate  with  silver  nitrate  independent  of  the 

presence  of  proteid  ? 
(7)  To  separate  peptone  from  other  proteids. — It  will  have 
been  noted  that  ammonium  sulphate  precipitates  all 
proteids  except  pure  peptone.  If  one  has  peptone 
mixed  with  proteoses  and  unchanged  proteids  one  may 
demonstrate  its  presence  by  precipitating  out  the  other 
proteids  and  then  demonstrating  by  such  a  test  as  the 
Biuret  test  the  presence  of  a  proteid  in  the  clear  fil- 
trate; that  could  be  nothing  else  than  peptone. 

Test  commercial  peptone  in  this  way  and  determine 
whether  any  appreciable  proportion  of  it  is  peptone. 
(#)    The  diffasibility    of  proteids.  —  Fill    seven    dialyzers 
with  the  proteids  above  studied. 

On  the  following  day  test  the  diffusates  for  proteids. 


XXXVII.    a.  Diffusibility  of  proteids. 
b.  Milk. 

a.   Diffusibility  of     proteids. 

/.   Materials. — -The   seven    dialyzers   filled  at    the    end    of 

the  previous  demonstration. 
2.  Experiments  and  Observations. 

( 1 )  What  reagent  may  best  be  used  to  determine  whether 
or  not  any  of  the  egg  albumin  has  diffused  through  the 
animal  membrane? 

(2)  How  may  one  determine  whether  or  not  any  of  the 
salts  of  the  egg  albumin  have  diffused  through  the 
membrane  ? 

(3)  In  the  case  of  the  saline  solution  of  myosin  (b),  of 
syntonin  (c)  and  of  acid  albumin  (d),  is  there  any  con- 
traindication against  silver  nitrate  as  a  reagent  to 
determine  whether  proteid  has  diffused? 

What  would  silver  nitrate  indicate  in  this  case  ? 

(4)  What  tests  would  be  most  reliable  in  these  cases  to 
detect  the  presence  of  proteid  in  the  diffusate  ? 

(5)  Would  a  trace  of  proteid  in  the  diffusate  necessarily 
demonstrate  the  diffusibility  of  these  proteids  through 
the  walls  of  the  alimentary  tract?     If  not;   why  not  ? 

(G)  What  tests  may  be  used  to  determine  the  presence 
of  gelatin  in  the  diffusate  ?     Is  gelati-n  diffusible? 

(7 )  The  term  proteoses  is  a  general  one  and  is  used  to 
designate  the  mid-products  of  proteid  digestion.  The 
mid-product  of  albumin  digestion  is  albumose;  of 
globulin  digestion,  globulose;  of  myosin,  myosinose; 
of  vitellin,  vitellinose;  of  casein,  caseinose;  or  in  gen- 
eral of  a  proteid,  proteose. 
166 


DIGESTION  AXD  ABSORPTION.  167 

Dialyzer  (f)  contains  products  of  peptic  digestion 
of  proteids — principally  albumin.  The  progress  of 
digestion  was  suspended  at  a  stage  when  there  were 
present  not  only  peptone  but  mid-products — albu- 
moses;  or,  to  use  the  general  term,  proteoses 

The  problem  which  confronts  us  is — to  determine 
whether  or  not  proteoses  are  diffusible. 

(a)  If  peptone  is  diffusible  the  diffusate  will  cer- 
tainly contain  peptone.  Do  peptone  and  the  pro- 
teoses respond  alike  to  all  the  general  tests  for 
proteids? 
(b.)  How  may  peptone  be  separated  from  the  pro- 
teoses ? 

What  single  reagent   is  indicated  in  the  case? 
(8)   Demonstrate  the  diffusibility  of  peptone. 
b.  Milk. 
/.   Materials. — One  liter   of  fresh  whole  milk;  one  liter  of 

milk  for  the  preparatory  steps  of  the  demonstration. 
2.  Preparation. 

(1)  On  the  day  before  the  demonstration  fill  a  500  c.  c. 
open  mouthed  cylinder  with  milk  and  put  it  in  a  cool 
place. 

(2)  Two  days  before  the  demonstration  weigh  out  10 
gm.  to  50  gm.  of  whole  milk  in  a  platinum  dish  or  in 
a  thin  porcelain  dish.  Place  it  in  a  drying  oven  at 
90°-95°C,  and  dry  to  constant  weight.  Record  the  dry 
weight. 

(3)  Before  the  hour  of  the  demonstration  burn  the  resi- 
due by  bringing  the  dish  which  contains  the  dry  solids 
to  a  red  glow  in  a  Bunsen  flame,  allowing  ample  access 
of  oxygen.  After  the  dish  and  the  white  ashes  have 
cooled  in  a  desiccator  take  the  weight.  All  of  these 
weights  should,  of  course,  be  taken  upon  an  analytical 
balance. 


168  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(4)   Fill  a  dialyzer  with  diluted   milk  one  day  before  the 
demonstration. 
J.   Experiments  and  Observations. 

(1)  What  proportion  of  milk  evaporates  at  the  tempera- 
ture above  suggested  ?  It  may  be  taken  for  granted 
that  this  proportion  represents  practically  the  water 
of  the  milk. 

(2)  Of  the  solids  of  milk  what  proportion  is  organic  and 
what  proportion  is  inorganic? 

(3)  What  bases  predominate  in  the  ashes?  [Let  a 
student  be  assigned  this  problem  for  solution.] 

(4)  What  is  the  character  of  the  organic  constituents  of 
milk? 

(a)  Note  that  the  milk  that  has  been  standing  has 
separated  into  two  layers,  an  upper  yellowish  layer 
and  a  lower  bluish  white  layer. 

(b)  Draw  off  with  pipette  a  few  cubic  centimeters  of 
the  cream  and  in  a  test  tube  add  an  equal  volume  of 
osmic  acid.  To  a  few  drops  of  olive  oil  in  another  tube 
add  osmic  acid.  Shake  both  tubes  vigorously.  Osmic 
acid  has  the  same  effect  upon  the  cream  as  upon  the 
olive  oil.  The  cream  is,  in  fact,  fat  in  physiological 
emulsion.  Quantitative  examination  shows  that 
about  4%  of  milk  or  4  13  of  the  solids  of  milk  con- 
sists of  fats  in  which  olein  predominates. 

(5)  Fill  a  siphon  with  water  and  introduce  it  through 
the  cream  to  the  bottom  of  the  500  c.c.  cylinder;  draw 
off  300  c.  c.  of  the  milk;  add  to  it  four  volumes  of 
water;  slowly  add  \(f0  acetic  acid  while  stirring  with  a 
rod,  until  the  casein  separates  as  a  copious  fiocculent 
precipitate.  After  the  casein  has  partially  settled  de- 
cant off  a  few  cubic  centimeters  of  the  supernatant 
liquid  and  subject  it  to  the  Fehling  test.  The  abun- 
dant precipitate  indicates  the  presence  of  a   reducing 


DIGESTION  AND  ABSORPTION.  169 

sugar.  It  is  milk  sugar  —  lactose.  About  4.4%  of 
milk  or  3/3  of  the  solid  matter  of  milk  is  lactose. 
(f>)  Wash  the  casein  by  the  repeated  addition  of  water, 
followed  by  decantation;  pour  it  into  a  linen  sack 
or  a  towel  and  press  out  the  water;  further  extract 
the  water  with  absolute  alcohol;  extract  the  remnant 
of  fat  with  ether;  dry  in  the  air.  The  white  granular 
material  that  remains  is  nearly  pure  casein,  the  most 
important  proteid  of  milk,  and  represents  nearly  4% 
of  milk. 

(7)  Heat  100  c.  c.of  the  fresh  milk  in  a  beaker.  Before 
the  boiling  point  is  reached  a  membrane  gathers  upon 
the  surface  of  the  milk.  This  membrane  represents 
the  lact-albumin  of  the  milk,  which  has  been  coagu- 
lated by  the  heat  and  has  collected  in  the  membranous 
coagulum  at  the  surface.  The  lact-albumin  repre- 
sents only  a  small  proportion  of  the  milk  proteid. 

(8)  To  30  c.  c.  of  fresh  milk  in  a  beaker  add  common 
salt  to  saturation.      Record  results. 

(9)  To  30  c.c.  of  fresh  milk  in  a  beaker  add  magnesium 
sulphate  to  saturation.      Record  results. 

(10)  Dilute  fresh  milk  to  one-fifth  normal  and  subject  it 
to  the  following  tests,  recording  results: 

(a)   The  iodine  test. 
(&)  Tromer's  test. 

(c)  The  xanthoproteic  test. 

(d)  The  Biuret  test. 

(/)   The  picric  acid  test. 
(/)  The  absolue  alcohol  test. 
(g)  The  osmic  acid  test. 

(11)  Fill  a  dialyzer  with  the  diluted  milk.  One  day 
later  examine  the  diffusate: 

(a)   For  any  of  the  inorganic  constituents  of  milk. 
(/>)   For  the  carbohydrate  constituents  of  milk. 


170  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(f)   For  the  proteid  constituents  of  milk. 
(//)   For  the  fatty  constituents  of  milk. 
(12)   Formulate  in   a   series  of   concise  statements   the 
facts  demonstrated  regarding  milk: 
(a)   Its  chemical  constituents. 
(<5)   Its  physical  properties. 
Why  should  milk  be  discussed  in  connection  with  the 
proteids  rather  than  with  the  carbohydrates;  considering 
that  the  proportion  of  carbohydrate  in  milk  is  greater  than 
that  of  proteid? 


XXXVIII.     Gastric  digestion. 

1.  Materials. — Two  fresh  pig-stomachs;  y2  Ko.  clean  sea 
sand;  4  eggs;  fibrin;  bread;  milk;  jellied  gelatin;  casein; 
rennin. 

2.  Preparation. 

( 1 )  To  prepare  artificial  gastric  juice. 

(a)  Stretch  a  fresh  stomach  of  a  pig  upon  a  board 
with  mucous  surface  up;  fix  with  nails. 

(^)  Rinse  off  the  mucous  membrane  gently  with  cold 
water. 

(c)  Scrape  thoroughly  with  a  dull  edged  table  knife, 
or  an  equivalent;  collect  the  scrapings  in  a  large 
mortar. 

(d)  Grind  the  scrapings  in  clean,  fine  sand. 

(<?)  Add  an  equal  volume  of  0.2%  HC1  and  leave  for 
24-48  hours,  stirring  occasionally. 

(/)  Strain  through  linen;  filter,  and  preserve  in  a  glass 
stoppered  bottle.  Label:  Acidulated  aqueous  extract 
of  pepsin. 

(g)  For  use  dilute  this  extract  with  three  or  four  vol- 
umes of  0.1%  HC1  (App.  A-17).  Label:  Artificial 
gastric  juice  (1). 

(2)  To  prepare  a  glycerin  extract  of  pepsin. 

(a)  Rinse  off  the  mucous  membrane  of  a  fresh  pig- 
stomach  with  cold  water  and  remove  the  mucous 
membrane  from  the  muscular  walls  of  the  stomach. 

(o)   Grind  the  mucous  membrane  in  the  meat  hasher. 

(<r)  Put  the  hashed  tissue  into  a  beaker  and  cover 
with  two  volumes  of   pure  glycerin.      Stir  the  mix- 

171 


172  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

ture  occasionally  for  several   days.       The  glycerin 

extracts  the  pepsin  ferment. 
(d)   Strain     the    glycerin    extract    through   fine    linen; 

preserve  in  a  glass  stoppered  bottle  for  future  use. 

It  will  keep  indefinitely. 
(^)   For  use  add  to   1   volume  of  the  extract  30  to  50 

volumes  of  0.2%  HC1.      Label:  Artif,  gast.  juice  (2). 
j.   Experiments  and  Observations. 

(1)  To  a  bit  of  starch  paste  of  the  consistency  of  jelly 
add  artificial  gastric  juice  (1);  place  in  the  incubator; 
in  ten  minutes  or  one  day  note  results.      Results? 

(2)  To  a  few  drops  of  olive  oil  or  to  a  bit  of  pure 
tallow  add  several  cubic  centimeters  of  gastric  juice 
and  keep  at  incubator  temperature  for  a  day.  What 
effect  has  gastric  digestion  upon  fat  or  oil  ? 

(3)  To  a  bit  of  pig  fat  add  gastric  juice  and  keep  at 
incubator  temperature  for  several  hours.  What 
effect  has  gastric   digestion  on  adipose  tissue  ? 

(4)  To  a  bit  of  fibrin  in  a  test  tube  add  gastric  juice. 
The  warmth  of  the  hand  will  be  sufficient.  If  the 
preparation  of  artificial  gastric  juice  has  been  suc- 
cessful, the  fibrin  will  dissolve  in  one  or  two  min- 
utes. One  may  be  certain  that  digestion  is  pro- 
gressing rapidly,  though  complete  solution  of  the 
fibrin  does  not  necessarily  indicate  complete  diges- 
tion of  it;  for  complete  digestion  of  a  proteid  im- 
plies that  the  food  stuff  in  question  is  both  dissolved 
and  diffusible.  The  fibrin  is  dissolved,  it  may  or 
may  not  be  diffusible.  But  this  will  be  determined 
later. 

(5)  To  determine  the  active  factors  of  gastric  digestion, 
(a)   To  a  few  shreds  of  fibrin  in  a  test  tube  add  a 

few  cubic  centimeters  of  0. 2  %  HC1.  Carefully  note 
results.     Will   dilute  HC1  dissolve  fibrin?     Is  it 


DIGESTION  AND  ABSORPTION.  173 

possible  to  digest  a  proteid  without  dissolving  it? 
(£)  To  fibrin  add  dilute  neutral  glycerin   extract  of 

pepsin.      Is  solution  affected  ? 
{/)  To  tube  (a)  add  a  few  drops  of  the  glycerin  extract 
of  pepsin. 

To    tube    (b)    add     2    volumes   of    0.2%    HC1. 
Note  results. 
(</)   Formulate  conclusions. 
(6)    To  determine   whether  the  acid  factor  of  gastric  diges- 
tion need  necessari/y  be  hydrochloric  acid. 

Prepare   a  0.4%    solution   of   each   of   the  following 
acids: 

(I)  Lactic  acid. 

(II)  Sulphuric  acid. 

(III)  Nitric  acid. 

(IV)  Phosphoric  acid. 

(V)  Citric  acid. 

(VI)  Acetic  acid. 

For  each  acid  prepare  four  test  tubes  as  follows: 
(I)   Lactic  acid. 

(a)   Fibrin  -flee.  glyc.  ext.  of  pepsin  -j-  10  c.c. 

0.4%  acid. 
(h)   Fibrin   +1    c.  c.  pepsin  ext.  -j-   10  c.  c.  0.2% 

acid. 

(c)  Fibrin  -flee,  pepsin  ext.   -(-   10    c.  c.    0  1% 
acid. 

(d)  Fibrin  -f-  1  c.  c.   pepsin  ext.  -f-  10  c.  c.  0.05% 
acid. 

Proceed  in  a  similar  manner  with  each  acid. 
Tabulate  results.  May  any  other  acid  or  acids 
take  the  place  of  HC1  as  a  factor  in  digestion  ? 
If  so,  in  what  minimum  strength?  Which  one  of 
the  above  acids  may   be   normally  present   in  the 


174  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

stomach?     May  any  of  the  above  acids  serve  as 
digestives  and  as  foods  ? 

As  digestives  and  as  tonics? 
As  digestives,  foods  and  tonics? 
Cite  authorities. 
(V)     To  determine     the    optimum    strength     of    the    hydro- 
chloric acid. 

Prepare  with  care  the  following  three  dilutions  of 
hydrochloric  acid:  10%,  1%,  0.1%.  [See  Appendix 
A,  17.] 

Into   twelve   test   tubes  put  as  many  small  masses 
of    fibrin;  into  each  tube  put   1   c.  c.   of  neutral   10% 
dilution  of    glycerin  extract  of  pepsin.     Label  and  fill 
tubes  as  follows: 
Tube  (a)   5%:   Add  to  the  fibrin  5   c.  c.  of   10%    HC1 

and  of   distilled  water  a  quantity  sufficient  to  make 

10  c.  c. 
Tube  (b)  2%:  Add  2  c.  c.  of  10%  HC1  and  aqua  dist. 

q.  s.  ad  10  c.  c. 
Tube  (c)  1%:   Add  1  c.  c.  of  10%  HC1  and  aqua  dist. 

q.  s.  ad  10  c.  c. 
Tube  (d)  0.5%:  Add  5  c.  c.  of   1%  HC1   and  aq.  dist. 

q.  s.  ad  10  c.  c. 
Tube  (e)  0.4%:   Add  4  c.  c.  of   1%    HC1  and   aq.  dist. 

q.  s.  ad  10  c.  c. 
Tube  (H  0.3%:   Add  3  c.  c.  of   1%  HC1  and  aq.   dist. 

q.  s.  ad   10  c.  c. 
Tube  (g)  0.2%:   Add  2  c.  c.  of   1%    HC1  and  aq.  dist. 

q.  s.  ad  10  c.  c. 
Tube  (h)  0.1%:   Add    1   c.  c.  of   1%  HC1  and  aq.  dist. 

q.  s.  ad  1 0  c.  c. 
Tube  (j)  0.05%:   Add  5  c.  c.  of  0. 1  %  HC1  and  aq.  dist. 

q.  s.  ad   10  c.  c. 


DIGESTION  AND  ABSORPTION.  175 

Tube  (k)  0.025%:   Add  -2.5  c.  c.  of  0.1%   HC1  and  aq. 

dist.  q.  s.  ad  10  c.  c. 
Tube  (1)  0.01%:  Add  1  c.  c.  of  0.1%  HC1  and  aq.  dist. 

q.  s.  ad   10  c.  c. 
Tube  (m)  0.005%:  Add  y2    c.  c.  of  0.1%    HC1  and   aq. 

dist.  q.  s.  ad  10  c.  c. 

Place  these  twelve  tubes  in  the  incubator  and  note 
conditions  every  10  minutes  for  the  first  hour,  every 
hour  for  the  first  six  hours  and  then  at  the  end  of  one 
or  two  days  make  the  final  observations. 

Tabulate  results.  Formulate  conclusions.  What 
range  of  strength  may,  from  the  experiments  with 
artificial  gastric  juice  under  artificial  conditions,  be 
considered  the  optimum  strength  for  the  acid?  Is 
there  any  reason  to  doubt  that  the  optimum  strength 
as  determined  above  is  essentially  different  from  the 
optimum  strength  in  normal  digestion  ? 
(8)  To  determine  how  dilute  the  pepsin  may  be  and  still 
be  efficient  in  digestion. 

This   experiment  requires    a    standard    solution    of 
pepsin  to  use   as  a  basis.     The  U.  S.  Pharmacopoeia 
(p.  295  of  the  7th  Decennial  Revision)  gives   the  fol- 
lowing formula  for  a  standard  solution  of  pepsin: 
Hydrochloric  acid  (absolute),  0.21  gm. 
Pepsin  (pure),  0  00335  gm. 
Water  (distilled),  q.  s.  ad  100  c.  c. 

The  following  suggestions  are  made  as  to  method 
of  preparation:  To  294  c.  c.  of  water  add  6  c.  c.  of 
dilute  hydrochloric  acid: — Sol.  A.* 

In  100  c.  c.  of  Sol.  A.  dissolve  0.067  gm.  of  standard 
pepsin: — Sol.  B.  To  95  c.  c.  of  Sol.  A  at  40°C.  add  5  c.  c. 

*HC1.  DIL.  contains  10^  of  Abs.  HC1.     The  C.  P.  muriatic  acid  of 
standard  Sp.  Gr.  contains  31.9$  Abs.  HC1. 


176  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

Sol.  B.  The  resulting  mixture  is  a  standard  artificial 
gastric  juice  of  the  formula  given  above,  and  has  the 
power  of  completely  digesting  at  38°-40°C  one-fifth  its 
weight    of    coagulated    egg    albumin    in    six    hours.* 

From  a  standard  gastric  juice  prepare  the  following 
dilutions  using  0.1%  HC1  as  a  diluent.  It  is  scarcely 
necessary  to  say  that  the  greatest  care  should  be 
taken,  (1)  to  make  all  measurements  with  preci- 
sion; and  (2)  to  thoroughly  shake  each  dilution  before 
drawing  off  the  material  for  the  next  lower  dilution. 
(a)   Standard  artificial    gastric  juice  10  c.  c.  -f- 1    c.  c. 

moist  fibrin. 
(#)    ^  standard  artificial  gastric  juice  10  c.  c.  +  l  c.  c. 

moist  fibrin. 
(0    i¥o    standard    artificial    gastric  juice  10   c.   c.-(-l 

c.  c.  moist  fibrin. 
(rtT)   l010„   standard   artificial    gastric   juice  10  c.    c.-f-l 

c.  c.  moist  fibrin. 
(e)    -fovuoo   standard  artificial   gastric  juice  10c.  c.-f-l 

c.  c.  moist  fibrin. 
(/)  ioo!ooo  standard  artificial  gastric  juice  10  c.  c.-f 

1  c.  c.  moist  fibrin 
Of)   t.ooo.ooo  standard  artificial  gastric  juice  10  c.  c.-f- 

1  c.  c.  moist  fibrin. 

Keep  tubes  in  incubator  or  water  bath  at  38°-40°C. 
Note  (1)  time  required  to  dissolve  fibrin  completely, 
(2)  time  required  to  change  all  acid  albumin  to  pro- 
teose or  peptone.  Will  one  millionth  standard  gastric 
juice  digest  fibrin  at  all?  Will  a  lower  dilution  (one 
ten-millionth)  digest  it;  if  so,  how  dilute,  and  how 
long  a  time  is  required? 


*For  details  of  testing  standard  gastric  juice  see  Pharmacopoeia. 


XXXIX.     Gastric  digestion,  continued. 

Experiments  and  observations,  continued. 

(9)  To  determine  the  influence  (if  the  hydrochloric  acid  of  the 
gastric  juice  upon  putrefaction  in  the  stomach. — It  has  been 
determined  that  the  hydrochloric  acid  in  the  stomach 
destroys,  under  favorable  conditions,  at  least  the  non- 
pathogenic forms  of  bacteria.  Let  us  determine  the 
strength  of  acid  necessary  to  destroy  the  common  bac- 
teria of  putrefaction.  To  each  tube  used  in  experiment 
(7)  add  a  minute  drop  of  any  putrefying  fluid.  If  the 
contents  of  a  tube  serve  as  a  good  culture  field  any  drop 
of  the  fluid  may  be  found  to  be  swarming  with  bacteria 
within  a  few  hours.  Within  a  few  hours  after  infect- 
ing the  tubes  examine  under  high  power — 700  to  1000 
diameters — a  drop  of  the  contents  of  each  tube. 
While  making  the  observations  take  care  not  to 
contaminate  one  tube  with  the  contents  of  another. 
That  the  tubes  containing  o°/c  or  2%  or  1  °]c  hydro- 
chloric acid  will  be  found  to  be  free  from  bacteria  goes 
without  saying.  Just  how  weak  may  the  acid  be  and 
destroy  the  bacteria?  How  weak  may  the  acid  be  and 
retard  their  development?  Could  one  readily  drink 
enough  liquid  at  a  meal  to  change  the  stomach  from  a 
sterilizing  field  to  a  culture  field  for  the  bacteria  of 
putrefaction  ? 

(10)  To  determine  the  influence  of  neutral  salts  upon  diges- 
tion.— Make  a  saturated  aqueous  solution  of  common 
salt;  also  \  sat.  sol,  and  T\  sat.  sol. 

(a)  To  R  c.c.   of  NaCl   sat.  sol.  add   1  c.c.  of  a  1% 

177 


178  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

HC1,  and  1  c.c.  glyc.  ext.  of  pepsin;  put  the  mix- 
ture into  a  test  tube;  label:  NaCl  sub.  saturated. 
Drop  in  a  bit  of  fibrin  and  put  into  the  incubator. 
Take  six  test  tubes,  provide  each  with  a  bit  of 
fibrin;  label  and  fill  each  as  follows: 
(£)  I  Sat.  NaCl  :  —  5  c.c.  artif.  gast.  juice  +  5  c.c. 
NaCl  sat. 

(c)  \  Sat.  NaCl  :  —  t>  c.c.  artif.  gast.  juice  +  2  c.c. 
NaCl  sat. 

(d)  I  Sat.  NaCl  :  —  5  c.c.  artif.  gast.  juice  +  5  c.c. 
NaCl  i  sat. 

(e)  -f\  Sat.  NaCl  :  —  <3  c.c.  artif.  gast.  juice  -f-  2  c.c. 
NaCl  J  sat. 

(/)    3V  Sat.  NaCl  :  —  5  c.c.  artif.  gast.  juice  +  5  c.c. 
NaCl  T\  sat. 

G>0   *V  Sat.  NaCl  :  —  ti  c.c.  artif.  gast.  juice  -f-  2  c.c. 
NaCl  TV  sat. 

What  fraction  of  saturation  with  table  salt  stops 
proteid  digestion  ?  Explain  its  action.  How 
much  NaCl  per  litre  would  that  represent  ?  Has 
this  any  hygienic  bearing? 

(11)  The  effect  of  mechanically  confining  the  fibrin  to  pre- 
vent its  swelling. — Tie  a  small  mass  of  fibrin  rather 
tightly  with  several  turns  of  white  thread;  drop  it  into 
a  test  tube  containing  artificial  gastric  juice;  put  the 
tube  into  the  incubator  and  watch  results. 

How  long  a  time  is  required   to  digest  the  fibrin? 
Has  this  any  hygienic  significance  ? 

(12)  The  influence  of  division  upon  the  time  required  to 
digest proteids. — Boil  an  egg  five  to  ten  minutes;  cool 
quickly;  separate  the  hard  coagulated  white  from  yolk 
and  envelopes. 


DIGESTION  AND  ABSORPTION.  179 

{a)   Cut  out  a  one  centimeter  cube  and  put  it  into  a 

beaker  with  40  c  c.  artificial  gastric  juice. 
(&)   Put  into  a  second  beaker  of  40  c.c.  gastric  juice 
a  centimeter  cube  which  has   been   divided    into 
eight  half-centimeter  cubes. 
(<r)   Prepare  another  beaker  in  which  are  16  quarter 
centimeter  cubes  in  10  c.c.  of  artificial  gastric  juice. 
(d)   Into  another  beaker  with  10  c.  c.  artificial  gastric 
juice  put  \  of  a  cubic  centimeter  of   the  egg  albu- 
min which  has    been   finely  divided    by  pressing 
through  a  fine  sieve. 

Note  time  required  in  each  case  to  completely 
digest  the  albumen. 

Has  this  any  hygienic  bearing  ? 
(13)    The  influence  of  temperature  upon  the  time  required  to 
digest proteids. — Prepare    five  tubes  by  first  providing 
each  with  5  c.c.  of  artificial   gastric  juice;    treat    the 
several  tubes  as  follows: 

(a)   Bring  to  60°C.  in  water  bath;    add  fibrin;    note 

time. 
(6)   Bring  to  50°C.  in  water  bath;    add  fibrin;  note 

time. 
(V)   Bring  to  30°C.  in  incubator;    add   fibrin;    note 
time. 

(d)  Leave  at  room  temperature  (20°C);  note  time. 

(e)  Bring  to  0°C.  in  ice  water;  add  fibrin;  note  time. 
What  is  the  optimum  temperature? 

Is  the  progress  of  digestion  materially  retarded 
by  a  reduction  of  the  temperature  ? 

Would  the  temperature  of  the  stomach  contents 
be  essentially  lowered  by  the  occasional  sipping 
of  an  iced  beverage  during  a  meal? 

What  is  the  hygienic  significance  of  the  experi- 
ment ? 


XL.  Gastric  digestion,  continued. 

J.    Experiments  and  Observations,  continued. 
(14  )    The  steps  of  gastric  digestion. 

Boil  an  egg  5  to  10  min.;  cool  quickly;  separate  out  the 
white;  press  it  through  a  fine  sieve;  put  into  a  beaker 
with  100  c.  c.  artif.  gastric  juice,  and  place  the  beaker 
in  a  water  bath  at  40°C.  At  intervals  of  2  minutes  for 
the  first  10  minutes;  then  at  intervals  of  5  minutes  for 
the  next  20  minutes;  then  at  intervals  of  10  minutes 
forthe  second  half  hour  and  after  that  at  intervals  of  one 
hour,  subject  the  liquid  to  tests  for  egg  albumin;  for 
acid  albumin;  for  albumose;  for  peptone.  In  what  order 
and  after  what  length  of  time  do  the  several  products 
appear?  Is  the  one  that  is  first  to  appear  also  first  to 
disappear  ? 
(15)    The  artificial  digestion  of  various  proteids. 

(a)  To  a  small    mass   of  jellied    gelatin  add   10  to   15 

volumes  of  artif.  gast.  juice,  and  note  effect. 
(£)  Subject    bread    to    the    xanthoproteic    test.      The 

presence  of  proteid  material  is  demonstrated.      Put 

a  small  piece  of  dry  bread  into  a  beaker  with  gastric 

juice,  and  note  effect. 

(c)  Note  the  course  of  casein  digestion. 

(d)  Triturate  in  a  mortar  well  cooked  lean  meat;  di- 
gest with  gastric  juice. 

(e)  Try  the  xanthoproteic  test  upon  cooked  beans  or 
peas;  proteid  is  present.  Triturate  in  a  mortar;  di- 
gest. 

(/)  In  each  case,  demonstrate  the  ultimate  appear- 
ance of  peptone. 

180 


DIGESTION  AND  ABSORPTION.  181 

(16)  The  artificial  digestion  of  milk. 

Of  fresh  milk  take  three  portions  of  5  c.  c.  each. 

(a)  To  one  portion  add  10  volumes  of  artif.  gast. 
juice;  and  place  it  in  the  incubator  at  38° — 40°C. 

(d)  Prepare  another  beaker  in  the  same  way  but 
place  it  in  a  water  bath  at  38° — 40°C.  and  keep  the 
mixture  well  stirred,  dividing  the  casein  coagulum 
as  fine  as  possible. 

(c)  Place  the  third  portion  of  milk  in  the  water 
bath.  When  it  has  become  warm  add  a  few  centi- 
grams of  rennin.  Fifteen  minutes  later  add  artif. 
gast.  juice.  Stir  as  in  (b.)  In  which  of  the  first 
two  does  digestion  seem  to  progress  the  more  rap- 
idly? Does  the  progress  or  process  of  the  digestion 
seem  to  be  materially  different  in  the  last  two  ex- 
periments, (b)  and  (c)  ?  Have  any  of  the  obser- 
vations made  on  milk  digestion  any  hygienic  sig- 
nificance ? 

(17)  The     diffusibility    of  the    products    of    the    artificial 
digestion  of  proteids. 

From  the  products  of  digestion  in  experiments 
(16-b)  digested  milk,  (15-a)  digested  gelatin,  (15-b) 
digested  bread,  and  (12  d)  digested  egg  albumun,  fill 
four  dialyzers — first  neutralizing  the  acid  with  sodic 
carbonate.  After  12-24  hours,  test  the  diffusate  for 
peptone.  Why  neutralize  the  liquid  before  filling  the 
dialyzer  ? 

Have  all  of  these  indiffusible  proteids  been  wholly 
or  in  part  changed  to  diffusible  peptones  by  the  action 
of  the  artif.  gast.  juice? 


XLI.  The  properties  of  fats. 

Materials. — Olive  oil;  cream;  butter;  beef  tallow;  lard; 
adipose  tissue;  cotton  seed  oil. 
Experiments  and  Observations. 

(1)  The  osmic  acid  test. — Place  in  test  tubes  a  small 
amount  of  each  of  the  above  food  stuffs;  add  to  each  a 
few  cubic  centimeters  of  osmic  acid.  A  characteristic 
reaction  takes  place,  the  result  of  which  is  a  deep 
brown  coloration  of  the  fat.  If  the  conditions  are 
favorable  the  stain  deepens  into  a  sepia  black.  The 
cream  and  the  adipose  tissue  have  proteid  admixtures; 
note  the  variation  of  the  reaction. 

(2)  The  solubility  of  fats  and  oils. — Prepare  three  tubes 
each  of  olive  oil,  of  cream,  and  of  tallow;  treat  each 
material  with  absolute  alcohol,  with  ether  and  with 
chloroform.  It  will  be  found  that  all  of  these  re- 
agents are  solvents  of  fats  and  oils.  The  alcohol, 
however,  dissolves  very  much  more  of  the  oil  or  fat 
when  warm  than  when  cold,  as  may  be  demonstrated 
by  making  the  alcoholic  solution  with  the  tube  im- 
mersed in  boiling  water;  after  the  alcohol  seems  to 
have  reached  the  limit  of  solution  at  that  temperature, 
immerse  the  tube  in  cold  water.  A  large  part  of  the 
dissolved  oil  instantly  separates  out,  but  will  readily 
redissolve  on  again  immersing  the  tube  in  the  boiling 
water. 

(3)  The  saponification  of  fats  and  oils. 

(a)  To  about  2  c.  c.  of  olive  oil  in  a  test  tube  add  1-2 
volumes  of  a  25%  solution  of  sodic  hydrate.  Shake 
the  mixture  vigorously;  it  is  evident  that  a  chemical 
reaction  is  in  progress.      The  fat  is  undergoing  the 

182 


DIGESTION  AND  ABSORPTION.  183 

process  of  saponification.  A  complete  and  typical 
saponification  requires  a  more  careful  apportion- 
ment of  the  amount  of  oil  and  of  alkali  used  and  an 
application  of  heat. 

(J>)  Repeat  the  experiment  substituting  a  25%  solu- 
tion of  potassic  hydrate.      The  result  is  similar. 

(V)  What  is  the  chemical  formula  of  palmitin?  Of 
stearin?    Of  olein  ? 

(d)  What  is  the  chemical  formula  of  palmitic  acid?  Of 
stearic  acid?     Of  oleic  acid  ? 

(<?)   Write  generalized  formulas  for  each  of  these  acids. 

(3)  Write  the  reaction  which  takes  place  in  saponifica- 
tion of  palmitin;  of  olein.  Note  the  ready  solubil- 
ity of  the  products  of  this  reaction  in  water. 

(4)  To  a  solution  of  soap  add  any  aqueous  solution  of  a 
calcium  salt  soluble  in  water,  e.  g.,  calcium  chloride — 
a  curdy  white  precipitate  separates  out.  Write  the 
formula  of  the  reaction. 

May  the  reaction   have  any  relation   to   hygiene  or 
therapeutics  ? 

(5)  The  emulsification  of  oils. — Gould  defines  an  emulsion 
as  "water  or  other  liquid  in  which  oil  in  minute  sub- 
division of  its  particles  is  suspended."  One  may  add, 
more  or  less  permanently  suspended.  For,  if  one  shake 
together  vigorously  2  c.  c.  of  oil  with  an  equal  amount 
of  water  in  a  test  tube  he  is  able  to  bring  about  a 
minute  subdivision  and  temporary  suspension  of  the 
oil  in  the  water.  While  the  oil  is  in  this  temporary 
physical  condition  it  has  the  white  color  typical  of 
emulsions  in  general.  In  a  few  minutes,  however, 
the  particles,  as  they  rise  to  the  top  of  the  liquid 
coalesce  into  minute  globules;  then  into  larger  and 
larger  globules  and  finally  into  a  homogeneous,  super- 
natant oil-layer. 


184  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(a)  Add  to  the  mixture  above  described  2  or  3  c.  c.  of 
strained  egg  albumin;  shake  vigorously.  One  ob- 
serves the  same  minute  subdivision  of  the  particles, 
but  they  show  no  tendency  to  coalesce  on  standing; 
the  suspension  is  "more  or  less  permanent." 

Why    do    not    the    particles    coalesce?     In    what 
respects  is  this  emulsion  unlike  milk  ? 

(b)  To  2  c.  c.  of  olive  oil  add  2  c.  c.  of  sirupy  solution 
of  any  gum,  e.  g.,  gum  acacia;  shake  the  mixture 
thoroughly.  An  emulsion  will  be  formed.  What 
characteristics  has  this  emulsion  in  common  with 
emulsion   (a)  ? 

(<r)  To  5  c.  c.  of  cotton  seed  oil  containing  a  little  free 
fatty  acid  add  10  drops  of  strong  sodium  carbonate 
solution  and  shake.  A  good  stable  emulsion  is 
made  in  this  way.  [Long's  Chemical  Physiology, 
p.  63.] 

In  what  way  is  this  emulsion  different  from  those 
which  precede  ?     Which  one  of  the  emulsions  given 
above  is  most  like  the  emulsions  formed  in  the  small 
intestine  ? 
(d)   What  matters  present  in  the  small  intestine  tend 
to  promote  emnlsification  of  fats  ? 
(G)    The  diffusibility  of  fats  or  their  derivatives  or  modifica- 
tions. 

Fill  five  dialyzers  as  follows: 
(a)   Milk. 

(d")  Solution  of  soap. 
(V)   10%  glycerine. 

(d)  Emulsion  (5-a). 

(e)  Emulsion  (5-c). 

Complete  the  observations  on  the  following  day,  deter 
mining  what  derivations  or  modifications  of  fat  or  oil  are 
diffusible.        How  may  the  presence  of  soap  in    the  dif- 
fusate  be  determined  ? 


MM.     Intestinal  digestion. 

Materials. — 2    pig   pancreases;   200   c.   c.   of   pig   or  ox 
bile. 

Preparation. 

(1)   Aqueous  pancreatic  extract  (a). 
[a)   Free  a  pig  pancreas  of  fat. 
{l>)   Grind  it  in  a  meat  hasher. 
(V)   Extract  with  water  kept  at  a  temperature  of  25° 

to  28°  C. 
(d)  After    two  hours  strain  through  linen    and    filter 
through  absorbent  cotton. 
(  2  )    Glycerin  extract  of  the  pancreatic  ferments. 
(a)   After  freeing  the  gland  of  fat,  grind  it. 
(6)   Place  it  in  two  volumes  of  absolute  alcohol  for  two 
days. 

(c)  Drain  off  the  alcohol  and  transfer  to  2  volumes  of 
pure  glycerin. 

(d)  After  one  week  press  out  the  glycerin,  which  has 
extracted  the  ferments. 

This  glycerin  extract  will  keep  indefinitely.      To 

make  artificial  pancreatic  jicice  proceed  as  follows: 

(/)   To  1  volume  of  the  glycerin   extract   add  5  or  G 

volumes   of  water   and  sufficient   sodium  carbonate 

solution  to  give  the  mixture    a    distinctly    alkaline 

reaction. 

(3.)   Preliminary  experiments  on  bile. — This  secretion  may 

be  easily  procured  from  the  slaughter  house  at  almost 

any  time  in  the  year,  whereas  the  gastric   juice  and 

pancreatic    juice  may  only  be  obtained    by  resort  to 

185 


186  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

operative  procedures  not  properly  in  the  field  of  this 
chapter.* 

(a)  To  diluted  bile  add  dilute  acetic  acid.  The 
copious  yellow  precipitate  is  mucin. 

(b)  To  diluted  bile  add  absolute  alcohol;  mucin  is 
precipitated;  filter.  To  one  portion  of  filtrate  add 
HC1.     The  yellow  precipitate  is  glycocholic  acid. 

"To  the  other  portion  of  the  filtrate  add  lead 
acetate,  which  throws  down  lead  glycocholate. 
Remove  this  by  filtration,  and  to  the  filtrate  add 
solution  of  basic  lead  acetate,  which  gives  a  further 
precipitation  of  lead  taurocholate." — [Chemical 
Physiology,  Long,  p.   119.] 

(c)  Gmeiin's  test  for  bile  pigments. — To  a  few  cubic 
centimeters  of  strong  nitric  acid  in  a  test  tube  care- 
fully add  dilute  bile.  At  the  junction  of  the  liquids 
a  play  of  colors,  green,  blue,  violet,  red  and  yellow, 
will  be  noted;  the  green  being  next  to  the  bile  and 
the  yellow  next  to  the  acid.  This  delicate  and  most 
reliable  test  may  be  applied  to  any  liquid  suspected 
of  containing  bile. 

(d)  The  reaction  of  bile  is  found  to  be  distinctly 
alkaline. 

j.    Experiments  and  Observations. 

a.    The  action  of  pancreatic  juice  upon  foods. 

(1)  To  raw  or  cooked  starch  add  in  one  beaker 
aqueous  extract  of  pancreas  (a);  in  another  add 
artificial  pancreatic  juice  (b);  place  the  mixtures  in 
the  incubator;  after  a  short  time  test  for  reducing 
sugar. 


*For  description  of  operations  for  the  establishment  of  gastric  fistulae, 
bilary  fistulas  and  pancreatic  fistulas,  see  Hand-book  for  Physiological 
Laboratory,   Sanderson,   pp.  475-517. 


DIGESTION  AND  ABSORPTIOl*.  18? 

Pancreatic  juice  contains  an  amylolytic  ferment. 

(2)  Subject  fibrin  to  the  action  of  both  of  the  pancre- 
atic preparations. 

Pancreatic  juice  contains  a  proteolytic  ferment. 

(3)  Boil  fresh  milk  and  mix  it  with  an  equal  bulk  of 
the  aqueous  extract  of  pancreas  and  put  the  mixture 
into  the  incubator.  Put  also  into  the  incubator 
boiled  milk  diluted  with  an  equal  volume  of  distilled 
water.  The  milk  which  is  mixed  with  pancreatic 
juice  will  curdle  much  sooner  than  the  other. 

Pancreatic  juice  contains  a  milk  curdling  ferment. 

(4)  Mix  5  or  G  c.  c.  of  neutral  olive  oil  with  an  equal 
volume  of  aqueous  extract  of  pancreas;  shake  the 
mixture  vigorously. 

No  emulsion  is  formed.  Place  one-half  of  the 
mixture  in  the  incubator.  After  a  few  hours  any 
undigested  oil  may  be  emulsionized  on  shaking,  or 
fresh  oil  may  be  emulsified.      Explain. 

(5)  To  the  second  part  of  the  mixture  add  3  c.  c.  bile; 
shake  the  mixture  vigorously.  A  good  emulsion  is 
formed.  How  is  this  emulsion  formed?  What 
factor  of  an  emulsion  does  the  bile  add  ?  What  is 
the  relation  of  experiment  (5)  to  experiment  (-1)? 

Pancreatic   juice    contains     a   fat-splitting  fermefit 
.  whose  action  liberates  fatty  acids. 

(6)  To  starch  paste  add  several  volumes  of  dilute 
bile.     Result? 

1^7)  To  fibrin  add  dilute  bile.      Result? 

(8)  To  oil  which  contains  free  fatty  acid  add  bile; 
shake  the  mixture  vigorously;     Result? 

(9)  To  neutral  oil  add  bile;  shake  the  mixture  vigor- 
ously. What  is  the  result?  Allow  the  mixture  to 
stand  in  the  incubator.  After  several  hours  shake 
the  mixture. 


188  LABOR  A  TOR  Y  G  UIDE  IN  PHYSIO  LOG  Y. 

Is  an  emulsion  formed? 
(10)  Summarize  the  results   of   the   foregoing  experi- 
ments, formulating  a  series  of  conclusions  regarding 
the  action  of  pancreatic  juice;  the  action  of  bile  and 
their  combined  action  on  each  class  of  food. 


XLIII.  Absorption. 

Physiologists  have  entertained  the  hope  that  all  the 
phenomena  of  absorption  of  diffusible  substances  could 
be  eventually  explained  by  the  laws  of  physics.  That 
hope  has  practically  given  place  to  the  conviction  that 
however  important  it  may  be  to  the  animal  economy  to 
produce,  in  its  digestive  processes,  diffusible  products, 
these  products  do  not  pass  through  the  epithelial  lining 
of  the  alimentary  tract  at  the  rate  or  in  the  propoitions 
that  would  be  observed  in  the  dialyzer.  This  need  oc- 
casion no  surprise;  in  one  case  we  have  to  deal  with 
living,  active  cells,  in  the  other  with  dead  tissue. 

Living  ceils  of  muscle-tissue  or  of  gland-tissue  have  the 
power  of  selecting  from  the  tissue  plasma  such  materials  as 
are  needed  for  the  replenishment  of  their  substance.  Not 
only  does  the  animal  select  what  shall  be  taken  into  the 
alimentary  tract  but  the  epithelial  lining  of  that  tract 
seems  to  select  what  shall  be  absorbed  and  to  absorb  it  ac- 
cording to  laws  which  conform  only  in  a  most  general  way 
or  which  may  not  conform  at  all  to  the  laws  of  osmosis. 
In  order,  however,  to  understand  the  current  literature  on 
the  subject  of  absorption  it  is  necessary  to  be  familiar  with 
the  terminology  and  laws  of  osmosis  and  dialysis.  To 
that  end  the  student  may  profitably  perform  for  himself  a 
few  simple  experiments  preliminary  to  more  complex  ones 
which  the  demonstrator  may  suggest  or  may  perform  for 
the  class. 

/.  Appliances  and  Materials. — Six  dialyzers    complete,  in- 
cluding outer  receptacles  and  supports;  2  or  3,  100  c.  c, 

189 


190  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

evaporating    dishes;  distilled    water;    sodium   chloride; 

alcohol;  egg;  mercury  manometer. 
2.  Preparation. 

(1.)  Fit  four  of  the  dialyzers  with  membrane  of  pig- 
bladder.  The  bladders  should  be  carefully  selected  as 
to  uniformity  in  thickness,  and  should  be  soaked  for 
an  hour  or  more  in  water  before  being  stretched  upon 
the  dialyzers.  The  membrane  should  be  stretched  as 
nearly  uniform  as  possible  upon  the  four  dialyzers. 
Fit  one  dialyzer  with  parchment  paper  such  as  is  fre- 
quently used  for  this  purpose.  Furnish  one  dialyzer 
with  some  other  animal  membrane  e.  g.,  a  cow's  blad- 
der or  a  rabbit's  caecum. 

(2)  Prepare  dilute  egg-albumin  by  adding  to  strained 
undiluted  albumin  about  9  volumes  of  distilled  water. 

j.   Experiments  and  Observations. 

(1)  Salt,  in  saturated  aqueous  solution  may  be  put 
into  a  dialyzer.  So  adjust  the  apparatus  that  the 
water  in  the  outer  receptacle  shall  be  on  a  level 
with  the  solution  in  the  vertical  tube  of  the  dialyzer. 
How  much  does  the  water  rise  in  the  tube?  What 
degree  of  positive  pressure  within  the  dialyzer  does 
that  represent?  How  much  pressure  per  unit  area, 
measured  with  a  mercury  manometer  will  it  be  nec- 
essary to  produce  within  the  dialyzer  to  stop  the  in- 
crease of  the  volume  of  its  contents?  (Endosmotie 
pressure.}  Will  that  amount  of  pressure  prohibit 
diffusion  between  the  liquids? 

(2)  After  osmosis  has  been  allowed  to  take  its  unim- 
peded course  for,  say,  one  hour,  starting  with  a  20  per 
cent,  solution  of  NaCl  within  and  distilled  water  with- 
out the  dialyzer,  note  the  height  of  the  water  in  the 
tube  and  compute  the  number  of  grammes  of  water 
which  have  entered   the    dialyzer.      Determine  how 


DIGESTION  AND  ABSORPTION.  191 

much  NaCl  has  passed  out  of  the  dialyzer.  An  easy 
and  sufficiently  accurate  method  is  to  evaporate  to 
dryness  all,  or  a  known  proportion  of  the  liquid  in 
the  outer  receptacle,  and  weigh  the  dry  salt  remain- 
ing. How  many  grammes  of  water  enter  the  dial- 
yzer for  each  gramme  of  salt  that  leaves  ?  ( Endos- 
motic  equivalent. ) 
I  3)  Is  the  endosmotic  equivalent  constant  for  salt  and 
water?  (a)  Is  it  the  same  for  different  strengths 
of  the  salt  solution,  i.  e.,  for  10%  or  1%  as  for  20%? 
(b)  Is  it  the  same  for  two  hours  or  four  hours  as 
for  one  hour  ? 

(4)  Fill  with  10%  glucose  three  dialyzers  provided  with 
three  different  kinds  of  membrane.  Does  osmosis 
take  place  at  the  same  rate  in  all  three  dialyzers  ? 
What  is  the  endosmotic  equivalent  for  glucose? 

(5)  What  is  the  endosmotic  equivalent  for  dilute  egg 
albumin?  When  albumin  is  injected  into  the  colon 
it  is  readily  absorbed  as  albumin,  there  being  no 
digestive  changes  in  it. 

(G)  Fill  a  dialyzer  with  equal  parts  of  10%  glucose 
and  10%  NaCl.  At  the  end  of  a  convenient  period, 
2-6  hours,  determine  whether  these  substances  have 
diffused  according  to  their  own  endosmotic  equiva- 
lents, i.  e.,  independent  of  each  other,  or  have  they 
been  influenced  the  one  by  the  other? 

(1)  Fill  a  dialyzer  with  alcohol.  Which  way  does  the 
osmotic  current  flow? 

(8)  In  the  above  experiments  water  has  uniformly 
passed  into  the  dialyzer.*  If  pure  water  be  taken 
into  an  empty  stomach  would  one  expect  it  to  be 
readily  absorbed  ?| 

*If  alcohol  be  taken  into  the  stomach  it  is  not  diluted  with  water 
drawn  from  the  tissue,  but  it  is  rapidly  absorbed. 

fWater  is  absorbed    slightly,   if   at    all,   through    the   walls  of    the 
stomach. 


F.    VISION. 


XLIV.     Dissection  of  the  appendages  of  the  eye. 

/.  Appliances. — Fresh  ox-eyes,  including  as  much  of  the 
appendages  as  possible;  physiological  operating  case; 
dissecting  boards  and  pins,  such  as  used  for  frogs;  dog, 
cat  or  rabbit;  bone  forceps;  injection  mass;  syringe. 

2.  Dissection.  -Follow  Gray;  or  Quain,  Vol.  III.,  Part  III. 
(1)  Before  fixing  the  eye  to  the  board  make  a  careful 
examination  of  the  organ. 

(a)  Trace  the  conjunctiva,  describing  its  ocular  and  its 
palpebral  portions.  Describe  the  plica  semilunaris 
and  the  caruncula.  Do  these  two  tissues  have  the 
same  relative  size  in  man  and  the  ox?  Find  and 
describe  the  puncta  lachrymalia.  Find  and  describe 
the  openings  of  the  lachrymal  ducts.  How  many  are 
there?  Enumerate  the  conjunctival  landmarks 
which  determine  the  inner  from  the  outer  side  of  the 
eye.  Enumerate  the  conjunctival  landmarks  which 
determine  the  superior  aspect  of  the  eye.  Is  the 
eye  which  you  have  a  right  or  a  left  one  ? 

(b)  Observe  the  appendages  of  the  eye.  Do  you  find 
a  remnant  of  the  levator  palpebrce  muscle  ?  Find 
the  tarsal  cartilages  and  the  remnant  of  the  orbicularis 
palpebrarum  muscle.    Find  openings  of  the  meibomian 

192 


VISION.  193 

and  of  sebaceous  glands.  Find  and  describe  the 
lachrymal  gland  as  to  location  and  size. 

Find  the  cut-off  ends  of  the  recti  and  oblique  mus- 
cles of  the  eye. 

Describe  the  location  of  the  optic  nerve  with 
respect  to  the  cornea. 

What  traces  have  you  found  of  the  capsule  of 
Tenon  ? 

Enumerate  the  new  landmarks  which  determine 
the  superior  aspect  of  the  eye;  the  internal  aspect. 
Are  these  extra  landmarks  sufficient  to  determine 
whether  the  eye  which  you  have  is  a  right  or  a 
left  one? 

(2)  Fix  the  eye  to  the  board  with  corneal  surface  down, 
pinning  down  flaps  of  the  conjunctiva  for  support. 

(a)  Dissect  out  the  four  recti  and  the  two  oblique  mus- 
cles. One  will  find  in  the  ox  a  rather  heavy  retractor 
muscle  in  close  relation  to  the  optic  nerve.  This 
should  be  left  undissected  until  the  other  muscles 
are  demonstrated. 

(b)  Trace  further  the  intricate  loculi  of  the  capsule  of 
Tenon. 

(V)  Carefully  separate  from  the  eyeball  all  connective 
and  adipose  tissue. 

(3)  Remove  the  retractor  muscle  of  the  ox  eye  in 
process  of  dissection,  taking  care  not  to  sever  any  im- 
portant blood  vessels  or  nerves. 

{a)  Locate  and  describe  the  vena  vorticosoz.  How 
many  are  there? 

(b)  Find  the  anterior  ciliary  arteries.  How  many  can 
be  found  ? 

Describe  their  relation  to  the  tendons  of  insertion 
of  the  recti  muscles.     What  tissues  do  they  supply? 

(c)  Find  the  two  long  ciliary  arteries. 


194  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(</)   Locate  and   enumerate   the  short  posterior  ciliary 

arteries. 
{e~)   Dissect  out   the  ciliary  nerves.      What   tissue    do 

they  supply? 

(4)  Let  one  number  of  the  division  dissect,  for  demon- 
stration, the  orbital  muscles  of  a  dog,  cat  or  rabbit. 
To  facilitate  the  dissection  fix  the  animal  with  dorsum 
up,  and  remove  with  bone  forceps  the  upper  and 
outer  walls  of  the  orbit. 

(5)  Let  one  member  of  the  division  inject,  with  carmine 
or  vermilion  mass,  the  internal  carotid  of  a  dog,  cat 
or  rabbit,  and  dissect  out  for  demonstration  the  ocular 
branches  of  the  ophthalmic  artery. 


XLV.  Dissection  of  the  eyeball. 

/.  Appliances. — The  eyes,  already  partly  dissected,  which 
have  been  kept  in  an  ice  chest;  physiological  operat- 
ing case. 

2.  Dissection. — a.  Anterior  dissection:  Fix  the  eye  to  the 
board,  cornea  upward,  using  the  dissected  muscles  as 
guys. 

(1)  Describe  the  cornea  as  seen  from  the  front.  Does 
the  radius  of  curvature  of  the  lateral  meridian  seem 
to  be  the  same  as  the  radius  of  curvature  of  the  ver- 
tical meridian?  With  heavy  scissors  remove  the  cor- 
nea, leaving  a  margin  of  one-eighth  inch  anterior  to 
its  junction  with  the  iris. 

Examine  the  cut  surface  of  the  cornea  with  a  lens. 

(2)  Through  the  elliptical  opening  thus  made  examine 
the  iris  as  to  texture,  etc. 

(3)  Holding  the  margin  of  the  cornea  with  strong  for- 
ceps, carefully  dissect  the  sclerotic  coat  from  the 
choroid  for  about  one  eighth  of  an  inch  posterior  to 
the  angle  of  the  anterior  chamber.  Locate  four  points 
in  the  margin  from  which  incisions  may  be  made 
antero-posteriorly  between  the  insertions  of  the  recti 
muscles.  From  the  points  located  make  the  incisions 
posteriorly  as  far  as  the  equator  of  the  eyeball.  Dis- 
sect each  flap  from  the  underlying  choroid;  remove 
the  pins  which  fix  the  recti  muscles,  and  through 
traction  draw  the  flaps  back;  fix. 

{a)   Make  a   drawing   of   the   choroid  with   its   irideal 
and  ciliary  portions  thus  exposed. 

195 


196  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

{b}  Locate,  if  possible,  the  course  and  distribution  of 
nerves  and  blood  vessels. 

(4)  With  fine  forceps  grasp  the  margin  of  the  iris  and 
with  fine  scissors  cut  out  a  sector  limited  posteriorly 
by  the  ciliary  body. 

(«)   Study  the  boundaries  of  the  posterior  chamber, 
(b)   Find  fibers  of  the  suspensory  ligament, 
{c)   Describe  the  anterior  surface    or  the  ciliary  proc- 
esses. 

(5)  Make  a  circular  incision  with  small  scissors  severing 
the  choroid  and  retina  at  about  the  line  of  the  ora 
serrata.  Lift  off  from  the  dense  vitreous  humor  the 
whole  ciliary  apparatus  and  lens,  place  them,  anterior 
surface  downward,  upon  a  plate. 

(a)  Describe  the  posterior  aspect  of  the  ciliary  proc- 
esses. 

(£)   Describe  the   lens  minutely,  as  viewed  externally. 

(<;)  Make  a  section  of  the  lens,  describe  its  appearance. 
Is  the  capsule  discernible  ? 

(6)  Describe  the  retina  as  seen  through  the  vitreous 
humor. 

(a)  Locate  the  entrance  of  the  optic  nerve. 

(b)  Can  the  fovea  centralis  be  located  ? 

(V)   Can  the  course  of  the  retinal  vessels  be  followed  ? 
2.  b.   Posterior  dissection. 

(7)  Let  one  member  of  the  division  remove  the  poste- 
rior half  of  the  sclerotic  coat,  after  first  fixing  the  eye 
with  cornea  downward,  using  the  recti  muscles,  in 
this  case  also,  for  guys. 

{a)   Note  the  vence  vorticoscz. 

(b)  Follow  the  ciliary  nerves  from  their  entrance  into 

the  eyeball,  along  their  course   between  the  sclerotic 

and  choroid  coats. 


/  7 SI  ON.  197 

(c)  Do  you  find  the  long  ciliary  arteries,  or  the  poste- 
rior ciliary  arteries  ? 

(8)  Remove  the  choroid  carefully. 

(a)   Note    the    character  of  its  tissue,    its  vascularity 

and  its  rich  pigmentation. 
(/')   Describe  the  retina  as  seen  from  this  direction.   Its 

pigmented    layer  has   probably  come  away  with  the 

choroid. 

(9)  Remove    the    posterior    half    of    the  vitreous    body 
together  with  the  retina. 

(0)  Make  a  drawing  of  the  posterior  surface  of  the  lens, 
suspensory  ligaments  and  ciliary  processes  as  shown 
posteriorly. 

(10)  Remove  the   remnant  of   the  vitreous    bod)';   sever 
the  fibers  of  the  suspensory  light;  lift  out  the  lens. 
(a)   Describe  the  ciliary  body  and  the  iris  thus  held  in 

their  normal  relations  by  the  supporting  sclera. 


XLVI.    Physiological  optics,    a.  Determination  of  indices 

of  refraction  of  water  and  of  glass,     b.   Determin= 

ation  of  focal  distance  of  lenses,     c.  Verifi= 

cation  of  formula:    -|  +  fv  =  p.     d.  A 

simple  dioptric  system. 

a.  Determination  of  the  indices  of  refraction  of  water 
and  of  glass. 

/.  Appliances. — Apparatus  for  determining  the  index  of  re- 
fraction; a  deep  flat-bottomed  water  pan;  a  cube  of 
glass  4-6  cm.  in  linear  dimensions  and  polished  on  at 
least  two  opposite  sides.  The  two  polished  sides  must 
be  absolutely  parallel,  whether  the  other  sides  are  par- 
allel makes  no  difference;  centimeter  rule  and  dividers. 

2.  Preparation. — A  very  convenient  and  sufficiently  exact 
apparatus  for  making  the  required  determination  may 
be  readily  made  as  follows: 

(1)  Take  a  carpenter's  tri-square,  constructed  wholly  of 
iron;  from  the  angle  x  (Fig.  26),  where  the  gradu- 
ated limb  joins  the  body,  measure  off  centimeters  upon 
the  inner  surface  of  the  body  and  cut  them  in  with  a 
file. 

(2)  Locate  on  the  inner  edge  of  the  graduated  limb  any 
point,  as  y,  6  to  9  centimeters  from  the  point  x. 
With  files  remove  about  y2  centimeter  of  the  edge  as 
indicated  in  the  figure,  cutting  deeply  at  z,  so  as  to 
leave  a  slender  point  at  y  as  indicated. 

(3)  Drill  a  hole  in  the  inner  surface  of  the  body  at  o; 
fit  and  drive  a  heavy  brass  or  iron  wire  into  this; 
sharpen  the  upper  end  of  the  wire.  The  length  of  the 
wire  above  the  body  must  be  two  or  three  centimeters 

198 


VISfON 


190 


greater  than  the  distance  x  y.      Bend  the  point  over  so 

that  the  distance  o  p  shall  equal  x  y. 
Experiments  and  Observations. — Place  the  instrument  in 
the  water  pan;  fill  the  pan,  so  adjusting  it  that  both 
points  p  and  y  will  just  touch  the  water,  or  rather  almost 
touch  the  water,  for  the  surface  of  the  water  at  y  must 
be  absolutely  plane.  If  the  point  touch  it  the  surface 
will  not  be  plane. 


Fig.  26. 

Fig.  26.      A  contrivance  for  use  in  determining  the  refractive  indices  of 
water  and  of  glass. 


(I)  (a)  Bring  a  small  rule  (r)  into  position  and  clamp 
it  to  the  limb  of  the  instrument  by  means  of  heavy 
serre-fine  forceps.  So  adjust  the  rule  that  as  one 
sights  along  its  upper  edge  the  points  a,  y  and  3  seem 
to  lie  in  one  and  the  same  straight   line.     Lift  the  ap- 


200  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

paratus  out  of   the  water  and   lay  it  upon   the  table, 

taking  care  not  to  disturb  the  adjustment. 

(/;)  With  dividers  measure  the  distance  from  the  point 
y  to  line  3.  This  is  the  radius.  Determine  the  point 
where  the  circumference  would  cut  the  upper  surface 
of  the  rule,  say  point  b. 

(V)  From  this  point  determine  the  perpendicular  dis- 
tance to  the  edge  of  the  limb  at  c. 

{it)  The  line  cyxis  a  normal  to  the  surface  of  the  water 
at  the  point  y.  The  angle  i  is  the  angle  of  incidence; 
the  angle  ris  the  angle  of  refraction.  Imagine  a  circle 
whose  center  is  at  y  and  whose  circumference  passes 
through  b  and  3.  The  line  b  c  is  the  sine  of  the  angle 
of  incidence.  The  line  x3  is  the  sine  of  the  angle 
of  refraction. 

(<?")  What  is  the  ratio  of    sin  i  to  sin   r,  or  ~—  =  ? 

v  J  '  sin  r 

(2)  In  the  same  manner  determine  the  ratio  of  the  sines 
of  these  angles  when  the  rule  is  so  adjusted  as  to 
bring  a'y  6   in  apparently  one  straight   line.     What  is 

the  ratio  of  sin  i '  to  sin  r '  ?  or  ~^,  =? 

sin  r 

(3)  If  the  instrument  has  been  carefully  constructed 
and  if  the  determination  has  been  made  with  suffi- 
cient care,  the  ratios  will   be  found   to  be  practically 

equal,   i.  e.,  5|5_?=5|ILL  .      What  is  the  constant  ratio  in 
^        '  '  sin  r      sin  r 

the  case  of  water?     This  constant  ratio  is  called   the 

index  of  refraction,  and  is  conventionally  represented 

by  ;j- 

For  water,  ft  =  Jjj^  =  |=  1.333. 

(4)  To  determine  the  index  of  refraction  of  glass  pro- 
ceed as  in  the  case  of  water.  Set  the  instrument  upon 
the  table;  the  block  of  glass  may  be  placed  upon  the 
body  of  the  instrument,  the  polished  surfaces  be- 
ing placed    above    and    below.       If    the  distance   be- 


VISION.  201 

tween  the  polished  surfaces  is  not  equal  to  x  y,  a  point 
y'  may  be  located  on  the  upper  surface  near  the  edge 
of  the  glass  block  by  making  a  dot  with  ink  where  the 
line  y  x  cuts  the  upper  surface  of  the  block.  This  line 
is  the  normal. 

What  is  the  index   of   refraction   of   the   glass  block 
furnished  by  the  demonstrator? 
b.  The  determination  of  the  focal  distance  of  lenses. 

By  means  of  a  spherometer  the  radius  of  curvature  (r) 
of  a  lens  may  be  determined.* 

If  one  knows  the  radius  of  curvature  of  a  lens  and  the 
index  of  refraction  of  the  material  of  which  the  lens  is 
made    he    may  compute   the  focal  distance   by  using   the 

formula  (1)  F  = — r  for  piano  convex  lenses,  or  (2)  F=z} ^ 

v    J  ,'J--l  r  v    J  2(,m-1) 

for   bi-convex   lenses.     But  there  is    an    easier  and   more 

direct  method  of  determining  the  focal  distance  of  a  lens; 

namely,  by  direct  experiment. 

/.  Appliances. — An  instrument  such  as  is  used  in  physical 
laboratories  for  the  same  purpose  or  such  a  one  as  is 
described  under  2;  several  lenses  ranging  from  5  cm.  to 
50  cm.  in  focal  distance. 

2.  Preparation. — A  most  satisfactory  apparatus  for  this 
purpose  may  be  made  by  any  student  or  demonstrator  in 
three  or  four  hours.  From  thin  pine  boards  construct  a 
simple  box  about  10  cm.  square  in  cross  section  by  50 
cm.  in  length.  One  end  of  the  box  should  be  closed 
with  a  tightly  stretched  oiled  paper  for  a  screen,  while 
the  other  end  may  be  closed  with  the  same  material  of 
which  the  rest  of  the  box  consists,  the  center  of  the  end 
having  a   circular  aperture  one  or  two  centimeters    in 

1-  cl 

*[r==fcH~2  ■  w^en  a=spherometer  reading,  and  l=the  length  of 
one  side  of  the  equilateral  triangle  determined  by  the  legs  of  the 
spherometer.] 


202 


LA  BORA  TOR  Y  G  UIDE  IN  PH  YSIOLOG 1 '. 


diameter.  The  bottom  of  the  box  is  constructed  as  fol- 
lows: (See  Fig.  2*7.)  Cut  through  the  middle  of  the  bot 
torn  a  slot  about  0.5  cm.  wide  and  45  cm.  long.  Make  a 
lens  carrier  of  wood  as  indicated  in  the  figure  (Fig.  27, 
C.  &  C'.).  The:  saw  groove  in  the  top  of  the  carrier 
serves  to  hold  the  lens.  If,  however,  the  lenses  to  be 
used  in  the  apparatus  be  not   provided  with  rims  and 


=* 


C 


Fig.  27. 

Fig.  27.     Showing  parts  of  apparatus  for  determining  the  focal  distance 
of  lenses.      For  construction  of  the  apparatus,  see  XLVI=b=2. 

rings  the  demonstrator  can  readily  contrive  a  means  of 
holding  them  in  place.  In  any  case  they  should  be  so 
held  that  the  plane  of  the  lens  is  perpendicular  to  the 
axis  of  the  box,  and  that  the  center  of  the  lens  (o) 
is  virtually  over  a  fixed  line  (o')  drawn  transverse  to  the 


VISION.  203 

axis  of  the  lens  carrier.  The  screws  S  and  S'  serve  the 
double  purpose  of  protecting  the  projection  (p)  from 
splitting  off  and  of  affording  handles  by  which  the  car- 
rier may  be  slipped  along  the  groove.  Along  one  edge 
of  the  groove  on  the  outer  surface  of  the  bottom  make  a 
centimeter  scale  carefully  with  a  sharp  hard  lead  pencil. 
The  scale  should  have  its  zero  point  in  the  plane  of  the 
screen.  At  the  point  D  fix  a  shaft  (such  a  one  as  shown  in 
Fig.  27,  D'),  which  shall  extend  several  centimeters  below 
the  bottom  and  set  perpendicular  to  it.  The  shaft  may 
be  fixed  in  a  universal  clamp-holder  and  the  whole  sup- 
ported upon  a  heavy  support.  By  adjusting  the  clamp- 
holder  the  apparatus  may  be  directed  toward  any  desired 
object.  Make  a  cover  to  the  box,  and  blacken  the  whole 
inside. 
?.  Observations. — Fix  a  lens  in  place;  close  the  box;  direct 
its  axis  toward  some  well  illuminated  distant  object; 
grasp  the  handles  of  the  lens  carrier  and  move  it  to  a 
position  which  gives  upon  the  screen  a  sharply  defined 
image  of  the  object  in  the  field.  One  has  only  to  read 
the  position  of  the  transverse  line  of  the  carrier  on  the 
centimeter  scale  to  have  the  focal  distance  of  the  lens; 
i.  e.,  the  distance  at  which  parallel  rays  are  focused. 
c.  Verification  of  the  formula  \  -4-  \  =  \. 

A  second  method  of  determining  the  focal  distance  of  a 
lens  depends  upon  the  relation  of  the  distances  of  the  conju- 
gate foci  to  the  general  focal  distance:  This  relation  may  be 
expressed  thus:  The  sum  of  the  reciprocals  of  the  conjugate 
foci  is  equal  to  the  reciprocal  of  the  focal  distance.  \-\-\~\' 
Now  when  a  lens  throws  upon  a  screen  the  image  of  an 
object  it  is  evident  that  the  distance  of  the  object  (o) 
represents  one  and  the  distance  of  the  image  (i)  represents 
the  other  of    these  conjugate  focal  distances;   so  one  may 


204 


LABORATORY  GU/DE  IN  PHYSIOLOGY. 


say:  The  reciprocal  of  the  distance  of  the  object  from  the  lens 
(  — )  plus  the  reciprocal  of  the  distance  of  the  image  (y) 
equals  the   reciprocal  of  the  general  focal  distance   ^:    thus 

(i  +  4"==4)-  This  formula  enables  one  to  compute 
the  focal  distance  after  first  determining  by  experiment  the 
values  o  and  i.  Inasmuch  as  the  student  has  already  deter- 
mined the  focal  distance  (F)  and  may  not  have  made  the 
rather  extended  computation  incident  to  the  derivation  of 
the  above  most  valuable  formula  it  is  considered  that  the 
most  profitable  course  to  pursue  at  this  point  is  the  verifi- 
cation of  the  formula. 


A 


\ 


c.,,/,.,,/....,..../....,..../....,..../....^,./....,....|....,....l,.,n,....^,..l,...|,...,l 


Fig.  28. 

Fig.  28.     An  apparatus  for  determining  the  conjugate  focal  distance 
For  description,  see  C=I. 

/.  Apparatus. — To  that  end  one  may  construct  a  simple 
apparatus  (Fig.  28).  For  the  determination  of  the  focal 
distance  it  is  usual  to  have  both  object  and  lens  mova- 
ble. For  our  purpose  this  may  be  dispensed  with  as  it 
lends  little  to  the  reliability  of  the  result  and  detracts 
much  from  the  simplicity  of  the  apparatus.  Upon  a 
thin  board  as  a  base  fix  an  upright  piece  near  one  end 
of  the  base,  whose  inner  surface  may  be  painted  white 
and   serve  as  a   screen  (S).      Near  the  other  end   fix  a 


VISION.  205 

second  upright  piece  having  in  its  center  a  large  hole. 
Over  this  hole,  on  the  inner  surface  of  the  upright,  fix  a 
sheet  of  lead  or  of  copper  in  which  some  figure  has  been 
cut  (o).  Construct  a  lens  carrier  (c),  whose  pointer  (p) 
will  indicate  upon  the  scale  (s')  the  position  of  the  center 
of  the  lens.  The  use  of  the  instrument  will  be  some- 
what facilitated  if  the  distance  between  the  surface  of 
the  screen  and  the  surface  of  the  lead  or  copper  be  pur- 
posely made  exactly  100  cm.  In  addition  to  the  above 
apparatus  one  needs  the  lenses  whose  focal  distance  he 
has  determined.  He  needs  also  a  lamp  or  candle  to 
place  behind  the  metallic  screen  at  e. 
Experiments  and  Observations. — Place  a  light  behind  the 
metallic  screen;  it  shines  through  the  figure  cut  through 
the  screen.      This  figure  is  the  object. 

(1)  (a)  Place  a  lens  in  the  carrier  and  so  adjust  it  that 
the  plane  which  it  represents  is  perpendicular  to  the 
axis  of  the  instrument  and  its  center  is  in  the  same 
perpendicular  plane  with  the  index  (p)  of  the  carrier. 

(b)  Slide  the  carrier  along  the  base  until  the  object  is 
sharply  focused  upon  the  screen. 

(c)  Read  from  the  scale  the  distance  of  the  lens  from 
the  image  (i).  If  the  instrument  is  made  just  100  cm. 
between  screen  and  object,  then  the  difference  be- 
tween 100  and  the  reading  will  be  the  distance  of  the 
lens  from  the  object.  Is  the  image  erect  or  inverted? 
Explain  the  phenomenon,  drawing  geometric  figure. 

(2)  Study  the  general  formula: 

w  l+\=r 

(b)    F=£n]  but  o+i  =  100;  therefore 
(Y)    100  F  =  o  i. 
From  this  form  of  the  statement  it  is  evident  that  the 


206  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

lens  will  throw  a  distinct  image  in  either  one  of  two 
positions.      Demonstrate  it  experimentally. 
(3)   Determine  o  and  i  for    each  lens  and  substituting 
their   values    and    that    of    F    previously  determined, 
verify  the  equation.     A    moderate    deviation    may  be 
expected,   due  to  errors  in  the  apparatus  and  in  the 
observations, 
(j)   Problems. 

The  value  of  the  formula   — \-—  =  tt  is  so  great  and 

O      '       1  1  ° 

its  application  so  frequent  that  the  student  should 
thoroughly  familiarize  himself  with  the   properties 
of  lenses  as  revealed  in  this  formula. 
Solve  the  following  problems: 

(1)  When  the  object  is  twice  the  focal  distance, 
what  is  the  distance  of  the  image  ? 

(2)  When  the  distance  of  the  object  is  greater 
than  2F,  how  does  the  distance  of  the  image  com- 
pare with  2F  ? 

(3)  When  the  object  is  at  a  very  great  distance 
(o=  oo)  at  what  distance  will  the  image  be  formed? 

(4)  What  is  the  maximum  focal  distance  that 
may  be  determined  or  verified  with  the  above  de- 
scribed apparatus  ?     Discuss  methodically. 

d.  A  simple  dioptric  system. 

The  simplest  dioptric  system  is  one  in  which  the  ray 
passes  from  one  medium  into  a  second  medium  of 
different  refractive  index,  the  surface  of  separation 
of  the  two  media  being  a  spherical  surface.  In  the 
accompanying  figure  (Fig.  29  A)  the  spherical  sur- 
face s'sps"  separates  the  medium  M,  whose  re- 
fractive index  is  1.000,  from  the  medium  M',  whose 
refractive  index  is  1.500. 

Note  the  following  cardinal  points  of  a  simple 
dioptric  system. 


VISION. 


207 


The  center  of  curvature  of  the  spherical  surface 
(n)  in  the  nodal  point. 

That  radius  which  is  the  center  of  symmetry  of 
the  dioptric  system  (e.  g.,  n — p.)  is  called  the  princi- 
pal axis  of  the  system.  In  this  axis  lie  the  first  and 
second  principal  foci,  f  and  f  respectively.  The  point 
where  the  optical  axis  cuts  the  spherical  surface 
(p)  is  called  the  principal  point.  The  plane  tangent 
to  the  spherical  surface  at  this  point  is  the  principal 


f 

* 

TV 

dy'-'~ 

~--.jc 

m' 

""---^^   .-" 

\  r 

"--. 

.  - 

r' 

c 

J 

r" ■ -^_^ 

~~— — V* 

n 

"T^ 

7 

\ 

A 

Fig.  29. 

Fig.  29.  A.  Showing  the  cardinal  points  of  a  simple  dioptric  sys- 
tem, n,  nodal  point;  R  p  n,  principal  axis;  p,  principal  point;  f,  f, 
principal  foci. 

Fig.  29.  B.  Showing  the  relation  of  the  visual  angle,  v  and  the 
size  of  object  and  image  to  values  p  and  n. 

plane.  Planes  perpendicular  to  the  optical  axis  at 
f  and  f'  are  called  the  first  and  second  principal  focal 
planes  respectively. 

Problem.  Given  the  radius  of  curvature  and  the 
index  of  refraction  to  locate  upon  the  principal  axis 
the  principal  foci. 

Neumann  has  given  the  following  construction: 


208  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(1)  Erect  at  n  and  p  perpendiculars  to  the  principal 
axis. 

(2)  Lay  off,  upon  each,  the  two  indices  of  refrac- 
tion of  the  two  media,  measured  from  the-  origin 
of  each  perpendicular,  in  the  same  linear  units 
used  in  measuring  the  radius.  In  the  figure  let 
n  c  and  p  d  represent  the  index  of  refraction  of 
the  medium  M,  and  n  a  and  p  b  the  index  of  re- 
fraction of  medium  M'.  The  continuation  of  line 
a  d  cuts  the  principal  axis  in  the  point  f,  the  first 
principal  focus,  while  the  line  b  c  cuts  it  in  the 
point  V,  the  second  principal  focus.  The  geo- 
metrical figure  shows  the  following  important 
properties  of  the  dioptric  system: 

I.  The  distance  from  the  first  principal  focus  to 
the  principal  point  equals  the  distance  from  the 
second  principal  focus  to  the  nodal  point. 

(1)  Mathematically  expressed:  pf=nf'. 

II.  The  ratio  of  the  second  focal  distance  (pP)  to 
the  first  (pf)  is  equal  to  the  ratio  of  the  index 
of  refraction  of  the  second  medium  (M')  to  that 
of  the  first  (M).* 

(2)  Mathematically  expressed: — pf:  pf'=/ji:  //'. 
But  pf  =  nf;  substitute  this  value  in  the  second 
equation, — 

(3)  ....  nf':  pf'=/r.  //';  assume  medium  M  to  have 
an  index  of  refraction  ,«=1. 

(4)  nf':pf'=:l://. 

(5)  pf'  =  nf'X,"';  or  more  concisely 

(5')  p    — //'n.      (See  p  and  n  in  Fig.  29.      A.) 

This   derived  property  of   the  construction  merits 
a  separate  formulation. 
♦Refraction  and  Accommodation  of  the  Eye. — Landolt,  p.  85. 


VISION.  209 

III.  The  distance  from  the  second  principal  focus 
to  the  principal  point  equals  the  product  of  the 
distance  from  that  focus  to  nodal  point  multi- 
plied by  the  index  of  refraction  of  the  second 
medium  (  p  =  «'n ). 

Note  in  addition  the  following  facts  regarding 
the  effect  of  such  a  dioptric  system  upon  light. 

1st.  The  ray  rs,  meeting  the  spherical  surface 
perpendicularly,  will  not  be  refracted  at  s,  but 
will  pass  on  through  the  nodal  point. 

2d.  The  ray  r's',  parallel  to  the  principal  axis  in 
the  first  medium  is  refracted  at  the  spherical  sur- 
face and  cuts  the  principal  axis  at  f, — it  passes 
through  the  second  principal  focus. 

3d.  The  ray  r"s",  cutting  the  principal  axis  at  f 
in  the  first  medium  (M),  is  refracted  at  s"  and 
traverses  the  second  medium  parallel  to  the  prin- 
cipal axis. 


XLVII.  Physiological  optics,  applied,     a.  The  application 

of  the  laws  of  refraction  to  the  mammalian  eye. 

b.    To   locate    in   the    mammalian    eye 

the  cardinal  points  of  the  sim= 

pie  dioptric  system. 

The  dissection  of  the  ox  eye  revealed  several  refractive 
media  (cornea,  aqueous  humor,  lens,  and  vitreous  humor) 
and  several  curved  surfaces  bounding  these  media.  In 
determining  the  focal  distance  of  a  lens  one  must  know  the 
radius  of  curvature  and  the  refractive  index.  In  determin- 
ing the  focal  distance  of  a  system  of  refractive  media  and 
surfaces  one  must  know  (1)  the  radius  of  curvature  of  each 
surface,  (2)  the  refractive  index  of  each  medium,  and  (3) 
the  location  of  their  cardinal  points  upon  the  principal 
axis  of  the  system. 

The  mammalian  eye  receives  its  light  through  media 
and  surfaces,  as  indicated  in  the  following  table: 


MEDIA. 

INDEX  OF 
REFRACTION. 

SURFACE. 

RADIUS 

Air. 
Tear  Film. 

1.000 

1.3365 

Over  Ant.  Surf.  Cornea. 

7.829+ cm. 

Cornea. 

1  3367 

Ant.  Corneal  Surface. 

7.8.'9+  cm. 

Aq    Humor. 

1  3365 

Post.   Corneal    Surface 

7.829— cm. 

Lens. 

1  4371 

Ant.  Surface. 

10  0  cm. 

Vit.  Humor. 

1.3365 

Post.  Surface. 

6  0  cm 

This  array  of  media  and  surfaces  would  seem  to  make 
a  problem  too  intricate  to  solve  with  the  means  at  our  dis- 
posal. Notice,  first  that  the  tear  film  and  the  ant.  and 
post,  corneal  surfaces  have  the  same  radius  of  curvature; 

210 


VISION.  211 

i.e.,  though  curved  surfaces  they  are  parallel  and  form  a 
case  under  the  following  theorem:  "If  a  ray  pass  from 
any  medium  through  a  denser  medium  which  is  bounded 
by  two  parallel  planes  it  emerges  from  the  denser  medium 
in  a  line  parallel  to  its  course  before  entering  that 
medium."  It  is  customary  at  this  point  to  take  the  ante- 
rior surface  of  the  cornea  as  the  first  refractive  surface 
and  /tt=1.8865. 

Notice  that  the  index  of  refraction  of  the  aqueous  humor 
and  vitreous  humor  are  the  same.  It  is  now  evident  that 
we  have  to  deal  with  three  media  [air,  aqueous  or  vitreous 
humor,  and  lens],  with  three  surfaces  [ant.  corneal  surface, 
ant.  and  post,  lens  surface],  whose  radii  are  7.829,  6  and 
10  respectively.  But  even  this  great  step  toward  simpli- 
fying the  problem  leaves  us  with  a  long  road  before  us  un- 
less we  can  find  a  short  cut.  "  It  has  been  shown  mathe- 
matically that  a  complex  optical  system  consisting  of  sev- 
eral surfaces  and  media,  centered  on  a  common  optical  axis, 
may  be  treated  as  if  it  consisted  of  two  surfaces  only." 
[Text-book  of  Physiology — Foster,  1891 — vol.  IV.,  pg.  9.] 
The  location  of  these  surfaces  and  the  cardinal  points  are 
given  as  follows  by  Landolt  : 

A.  The  norma/  eye. 

The  point  r  (Fig.  30.)  where  the  principal  axis  cuts  the 
cornea  is  22.8237  mm.  from  the  second  principal  focus  V 
(the  retina) ;  c,  the  center  of  curvature  of  the  cornea;  s,  the 
point  where  the  optical  axis  cuts  the  anterior  surface  of 
the  lens,  is  3.6  mm.  from  r,  the  point  where  the  optical 
axis  cuts  the  posterior  surface  of  the  lens  7.2  mm.  from 
r;  1,  the  center  of  curvature  of  ant.  surface  of  lens;  1', 
the  center  of  curvature  of  posterior  surface  of  lens. 

B.  The  accurate  mathematical  reduction. 

The  reduction  referred  to  in  the  text  above  is  represented 
by  the  two  refractive  surfaces  with  nodal  points  n  and  n' 


212 


LABOR  A  TOR  Y  G  UIDE  IN  PH  \  S/OL  O  G  Y. 


radii  of  5.215  mm.  each  and  cutting  the  optical  axis  at  p 
and  p',  located    1.7532    mm.   and    2. 11  mm.  respectively 
from  r. 
C.    The  final  approximate  reduction. 

Note  that  p  is  less  than  0.36  mm.  from  p'.  One  may  as- 
sume one  nodal  point  N,  and  one  refracting  surface  between 
the  computed  ones,  cutting  the  principal  axis  at  P,  and 
introduce  an  error  too  slight  to  consider.  But  this  brings 


^piu>6c^ 


f 


Fig.  30. 

Fig.  30.  Showing  the  mathematical  features  of  the  reducea  eye. 
For  detailed  explanation  of  the  figure  see  text  A,  B  and  C.  The  figure 
is  multiplied  by  five  in  its  linear  dimensions.  [Errata  :  For  G  cm  read 
3  cm] 

us   back   to   the  simplest  possible  dioptric  system,   already 
described  on  pg.  206  et.  sea. 

All  of  the  properties  of  that    simple   dioptric  system 
are  possessed  by  the  normal  mammalian  eye. 
b.  To  locate,  experimentally  in  the  mammalian  eye,  the 

cardinal  points  of  the  simple  dioptric  system. 
/.  Appliances  and  Materials. — A  white  rabbit;  support  with 
universal    clamp-holder    and    small    cork-lined    burette 


VISION.  213 

clamps;  meter  stick  or  tape;  steel  or  ivory  rule,  with 
millimeters  subdivided  if  possible,  hand  lens,  fine  divid- 
ers with  needle  points;  bone  forceps;  NaClO.6%;  camel's 
hair  pencil;  absorbent  cotton. 
2.  Preparation. — (1)  Mathematical.  (See  Fig.  29  B.) 
We  wish  first  to  locate  the  nodal  point  in  a  rabbit's  eye. 
Represent  the  distance  from  the  retina  to  the  nodal 
point  by  n,  the  distance  from  the  object  to  the  image  by 
d,  the  vertical  dimension  of  the  object  by  o,  the  same 
dimension  of  the  image  by  i.  From  the  similar  right 
triangles  of  the  figure  one  ma}'  write: 

(1)  o:  i  =  d — n:  n; 

(2)  on  =  id — in; 

(») » =& 

Jnder  the  conditions  of  the  experiment  i  is  so  small 
compared  with  o  that  it  may  be  ignored  in  the  denomi- 
nator, and  we   may  use  the  equation: 

(4)    n  =  '-d. 

v    '  o 

(2)   Arrangement  of  Apparatus. 

{a)  A  convenient  object  to  observe  is  a  well-illumi- 
nated window,  or  one  sash  of  a  window;  measure 
the  vertical  distance  between  the  horizontal  strips 
of  the  sash. 

{b)  Arrange  three  or  four  tables  end  to  end  in  a  line 
perpendicular  to  the   plane   of  a  window.      On  the 
table  lay  off  from  the  plane  of  the  window  the  dis- 
tances 4,  4.5,  5,  5.5  and  G  meters. 
J.    Operation. 

(1)  Remove  an  eye  from  the  rabbit  which  had  been 
chloroformed  some  time  before  and  suspended  by  the 
anterior  limbs. 

(2)  Dissect   from  the  eye,  especially  from   the  posterior 


214  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

aspect  of  it,  all  of  the  areolar  connective  tissue,  muscle 
tissue,  etc.,  down  to  the  glistening  smooth  sclera. 

(3)  Wrap  around  its  equator  a  band  of  absorbent  cot- 
ton wet  with  normal  solution. 

(4)  Fix  the  eye  in  the  clamp  with  its  axis  transverse  to 
the  axis  of  the  clamp,  t?king  care  to  exert  just  enough 
pressure  to  prevent  the  eye  from  falling  on  being 
touched,  but  not  enough  to  distort  it. 

(5)  Fix  to  the  clamp  a  thread  with  a  bit  of  lead  to  serve 
as  a  plumb  line. 

4.    Observations. 

(1)  Adjust  the  support  so  that  the  eye  is  directed  toward 
the  object  and  the  image  is  located  approximately 
symmetrically  about  the  fovea  centralis,  and  the  plumb 
line  over  the  mark  4  meters.  With  the  fine  dividers 
measure  in  the  image  the  distance  between  those 
points  which  were  chosen  as  the  limits  of  the  object. 
The  value  of  this  measurement  may  be  read  to  tenths 
of  millimeters  by  laying  the  divider  points  upon  the 
steel  rule  and  reading  with  the  hand  lens. 

(2)  Make  similar  observations  at  4.5  m.,  5  m.,  5.5  m., 
and  6  m.  Each  observation  should  be  made  three  or 
four  times  and  the  average  taken. 

(b)  Record  these  averages  in  a  table  ruled  with  columns 
for  the  values  d,  o,  i,  n  and  /. 

(4)  Calculate  for  column  n  the  values  obtained  by  sub- 
stituting, in  the  formula  n  —  ~,  the  values  observed  in 
(1)  and  (2).      What  is  the  value  of  n  ? 

(5)  Measure  the  antero-posterior  diameter  of  the  eye. 
How  far  anterior  to  the  posterior  surface  of  the  sclera 
is  n  located?  How  far  from  the  surface  of  the  cornea? 
How  does  the  ratio  of  these  two  quantities  differ  from 
that  given  above  for  the  human  eye? 

(6)  Locate  the   position   of   the   principal   point   or   the 


VISION.  215 

point  where  the  ideal  refracting  surface  of  the  eye 
cuts  the  optical  axis,  by  applying  the  formula: 
p=/m. 
Assuming  for  ft  the  value  which  it  has  been  calculated 
to  have  in  the  human  eye  (1.3365  Landolt,  p.  8(j), 
how  far  is  this  point  posterior  to  the  anterior  surface 
of  the  cornea  ?  How  does  your  result  compare  with 
that  for  the  "  reduced  human  eye?  " 

(7)  Is  the  image  erect  or  inverted?  Explain  the  phe- 
nomenon ? 

(8)  Move  the  eye  to  within  one  meter  of  the  object. 
Note  that  a  fairly  clear  image  may  be  thrown  upon  a 
posterior  segment  of  the  sphere,  which  is  many  hun- 
dred times  the  area  of  the  fovea  centralis. 

(9)  If  a  fine  sharp  needle  be  thrust  through  the  eyeball, 
following  a  course  perpendicular  to  the  optical  axis 
and  cutting  it  at  n,  what  relation  would  this  needle 
have  with  the  lens  ?  Would  it  be  tangent  to  the  lens; 
would  it  enter  the  lens  or  would  it  pass  free  of  its  pos- 
terior surface? 

(10)  If  a  similar  experiment  were  performed  with  refer- 
ence to  the  point  p,  what  relation  would  the  needle 
have  to  the  anterior  surface  of  the  lens  ? 

For  these  experiments  the  eye  may  be  frozen  after 
the  introduction  of  the  needle  and  a  vertical  longi- 
tudinal section  made. 


XLVIII.     Accommodation  and  convergence. 

In  the  above  experiment  with  the  excised  rabbit's  eye 
one  notices  a  marked  blurring  of  the  image  when  the  eye 
is  brought  near  the  object.  Though  the  definition  of  the 
image  is  sharp  at  5-6  meters  or  beyond,  at  2  or  3  meters 
the  outlines  are  hazy.  The  normal  living  eye  is,  however, 
able  to  give  one  the  sensation  of  a  clear  image  at  any  distance 
from  several  inches  to  several  miles.  That  there  is  actually 
a  sharply  defined  image  upon  the  retina  when  the  normal 
mind  has  the  sensation  of  such  an  image  there  is  no  doubt. 
One  knows  from  his  experience  with  optical  instruments 
that  they  must  be  readjusted  for  each  distance  if  they  are 
to  yield  a  sharp  image  for  each  distance. 

The  same  thing  is  true  in  the  case  of  the  organic  optical 
instruments  with  which  one  perceives  the  form,  color  and 
space  relations  of  the  objects  of  his  environment.  The 
functional  adaptation  of  the  visual  organs  to  distance  is  called 
accommoda  Hon . 
a.  Accommodation. 
Experiments  and  Observations. 

(1)  Take  a  sharp  pointed  pencil  or  similar  object  in  each 
hand]  hold  the  upturned  points  in  the  line  of  direct 
vision  before  the  eye,  one  point  being  about  25  centi- 
meters distant  from  the  eye  and  the  other  at  arm's 
length;  make  the  observations  with  one  eye,  the  other 
being  closed  or  screened, 
(a)   Focus  upon  the  near  point.      Is  the  image  of   the 

distant  point  clear? 
(/;)    Focus  upon    the  distant    point.      Is   the  image  of 
the  near  point  clear? 

216 


\IS  ION.  217 

(r)  While  the  eye  is  focused  steadily  upon  the  near 
point  bring  the  distant  point  slowly  up  to  a  position 
beside  the  near  point.  One  of  the  images  is  trans 
formed  from  an  ill  defined  one  to  a  clearly  defined 
one.  Which  image  is  it  ?  Does  one  note  a  similar 
change  in  the  definition  of  the  image  when  he 
moves  the  near  point  out  to  position  beside  the  dis- 
tant point  while  focusing  steadily  at  the  latter? 

(d)  Sum  up  the  results  of  the  experiment  into  a  con- 
cisely formulated  statement. 

(2)   Holding  the  two  points  side  by  side  at  a  distance  of 

30  centimeters   note   that    the   points  appear  equally 

well  defined. 

(a)  Direct  the  eye  steadily  at  one  of  the  points  while 
moving  the  other  one  nearer  to  the  eye.  Note  the 
number  of  centimeters  which  it  advances  toward  the 
eye  before  the  outlines  become  ill-defined.  Reverse 
the  act,  moving  the  point  back  to  its  original  posi- 
tion beside  the  stationary  point,  noting  that  the 
image  of  the  receding  point  remains  clear. 

(£)  Continue  to  carry  it  farther  from  the  eye,  noting 
that  after  it  has  been  carried  beyond  the  unmoved 
focused  point  a  certain  distance  the  outline  be- 
comes again  ill-defined.  Note  the  number  of  centi- 
meters between  the  two  points  in  this  position. 

( c)  Make  a  similar  experiment,  using  50  cm.  for 
the  distance  of  the  stationary  point,  and  note  the 
centimeters  between  the  points  at  the  limits  of 
clear  definition.  In  this  way  one  may  observe  and 
measure  the  depth  of  focus  of  the  eye. 

(//)  Is  the  depth  of  focus  greater  at  30  cm.  or  at 
50  cm.  ? 

(e)  Is  the  depth  of  focus  greater  at  100  meters  than  at 
one  meter  ?     Demonstrate  and  explain. 


218  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

i  3  )  Deter  initiation  of  the  near  point  or  "punctum  prox- 
imum."  Determine  the  distance  from  the  eye  of  the 
nearest  point  at  which  a  pencil  point  or  needle  may 
be  perfectly  clearly  seen.  The  exact  location  of  the 
near  point  may  be  more  satisfactorily  determined  if 
one  look  at  the  object  through  two  holes,  2  mm.  apart, 
in  a  card.  At  this  point  thepunctum  proximum  act 
of  accommodation  is  brought  most  actively  into  play. 

(4)   Determination  of  the  punctum  remotum. 

(a)  Direct  the  eye  toward  some  object  not  less  than 
six  meters  away  and  describe  to  other  members  of 
the  division  the  minute  details  of  the  object,  such  as 
slight  irregularities  of  surface  lines  or  other  details. 
If  an  individual  is  able  to  convince  his  comrades  that 
he  can  perceive,  at  this  distance  the  minute  details 
of  objects  he  must  be  credited  with  normal  vision. 
Inasmuch  as  he  can  also  see  with  the  usual  distinc- 
tions more  distant  objects  the  punctum  remotum  is 
said  to  be  located  at  infinity;  or,  to  state  it  in  another 
way,  the  eye  is  able,  with  suspended  accommodation, 
to  bring  parallel  rays  to  a  focus  upon  the  retina.* 
{b~)  It  frequently  happens  that  the  individual  under 
observation  fails  to  make  out  more  than  the  merest 
outline  of  an  object  6  meters  away.  Decrease  the 
distance  until  he  is  able  to  perceive  details  seen  by 
the  majority  of  his  comrades.  If  this  distance  has 
to  be  decreased  to  two  or  three  meters  the  determi- 
nation may  be  made  more  exact  by  resorting  again 
to  the  needle  and  punctured  card  mentioned  in  (a), 
and  carrying  the  needle  away  until  it  appears  double. 

*  It  must  be  stated  here  that  this  experiment  does  not  make  it  cer- 
tain that  the  punctum  remotum  is  not  beyond  infinity!  In  a  subsequent 
lesion  that  point  will  be  carried  farther.  We  must  be  temporarily  con- 
tent with  having  it  so  far. 


VIS  I  OX.  219 

In  recording  the  punctum  remotum,  write  infinity  (oo  ) 
for  six  meters  or  more  and  for  any  distance  within 
that,  record  in  meters  and  decimals  thereof. 

(5)  How  many  meters  from  the  punctum  remotum  to  the 
punctum  proximum  in  those  cases  where  the  punctum 
remotum  is  less  than  six  meters  ? 

(6)  Observe  the  pupil  closely  while  the  subject  directs 
the  eye  from  a  distant  object  to  a  near  one.  It  con- 
tracts slightly.  On  a  priori  grounds  this  act  of  the 
iris  is  advantageous.  Showfrom  the  standpoint  of  the- 
oretical  optics  why  it  is  advantageous. 

(7)  Observe    from  the  side  that  when  the  act  of  accom- 
modation takes  place  the  iris  at  the  edge  of  the  pupil 
not  only  moves  toward  the  center  but  advances  notice- 
ably toward  the  cornea.      What  could  produce  this? 
(a)  If  the  edge  of  the  iris  rests  upon  the  lens  capsule 

would  it  not  be  pushed  farther  toward  the  cornea 
incident  to  its  contraction  toward  the  center? 

If  the  pupil  contracted  from  a  3  mm.  diameter  to 
a  2  mm.  diameter,  how  much  would  it  be  advanced 
incident  to  the  normal  curvature  of  the  lens.  Could 
this  be  detected  by  the  method  of  observation  which 
has  been  employed  ? 
(o)  Account  for  the  forward  movement  of  the  pupillary 
edge  of  the  iris  during  accommodation. 
b.  Adaptation  of  the  eye  for  direction.     Convergence. 

Just  as  the  eye  possesses  a  mechanism  by  which  it 
changes  its  refractive  power  for  different  distances,  so  it 
possesses  a  mechanism  by  which  it  may  change  the  direc- 
tion of  its  visual  axis  from  one  object  to  another  or  may 
follow  the  movements  of  objects  within  the  range  of  vision. 
I.  Monocular  fixation. — Let  two  individuals  work  together, 
one  as  subject  and  the  other  as  observer.      Let  them  sit 


220  LABORATORY  GUIDE  IN  P/fVSfOLOGY. 

on  opposite  sides  of  the  table.  Let  the  subject  close  or 
screen  one  eye. 

(1)  Hold  any  object  directly  in  front  of  the  subject;  let 
the  subject  keep  his  gaze  continually  fixed  upon  the 
object.  Move  the  object  quickly  toward  the  subject's 
left,  and  note  the  fixation  anew  of  the  object  in  its  new 
position.  What  muscle  or  muscles  accomplished  this 
act  of  monocular  fixation? 

(2)  Move  the  object  quickly  in  the  opposite  direction, 
then  upward,  downward  and  diagonally,  noting  the 
instantaneous  adaption  of  the  eye  to  the  new 
direction,  recording  also  the  muscle  or  muscles  involved 
in  each  act.  Are  all  the  movements  apparently  equally 
ready  and  exact  ? 

(3)  Bringing  the  object  to  a  point  directly  in  front,  1  m. 
distant,  note  through  how  great  a  lateral  movement  it 
may  be  carried  without  inducing  any  discernible  change 
in  the  visual  axis  of  the  eye. 

(4)  Bring  the  object  to  the  central  position  and  move  it 
very  slowly  outward  in  any  direction,  noting  whether 
the  changes  in  the  direction  of  the  visual  axis  are 
equally  slow  and  regular. 

2.  Binocular  fixation,  convergence. 

In  the  above  experiments  it  was  probably  noted  by  both 
subject  and  observer  that  the  closed  or  screened  eye 
responded  to  every  movement  of  the  other  eye. 

(5)  With  both  eyes  open  and  fixed  upon  an  object  held 
directly  in  front  at  a  distance  of  about  1  m.,  let  the 
observer  move  the  object  quickly,  then  slowly,  right, 
left,  up,  down,  and  around,  and  observe  the  continuous 
perfect  fixation  of  the  object  with  both  eyes. 

(a)  "What  muscles  are  involved  in  following  an  object 
from  one's  right  side  to  his  left  ?  In  each  other  di- 
rection in  turn? 


VISION.  221 

(/>)   Do  all  of  these  muscles   seem  to  act  perfectly  in 

all  of  the  subjects  examined?     If  not;  describe  any 

variation. 
(6)  Convergence,  (a)  Let  the  subject  direct  his  gaze  at 
the  tip  of  the  observer's  ear,  and  without  warning 
change  his  point  of  binocular  fixation  to  some  distant 
object  in  the  same  line  of  vision.  What  change  in 
the  eyes  of  the  subject  is  noticeable  by  the  observer  ? 
What  muscles  were  involved  in  producing  the  change  ? 
(/>)   Hold  an  object  in   front  of  the  subject  and  1   m. 

distant.      Move  it  directly  toward  the  subject's  eyes 

and  note  the  convergence  of  the  lines  of  vision  of 

the  two  eyes.      What  muscles  perform  the  act  ? 
(/)   Through   how  short  a  distance  may  the  object  be 

moved  in  the  direct  line  of  vision  without  causing  a 

discernible   change  of  the   angle  of   convergence  of 

the  two  eyes. 
(d)   From  the  central,  1  m.    position,  carry   the  object 

to  a   point  about    }4    rn.    to   the   right,  and    }4    m. 

above  the  eyes   of  the  subject.     What   muscles  are 

involved  in  the  act  of  convergence  ? 
(^)  Is  the  power  of  convergence  apparently  normal  in 

all  members  of  the  class  ?     If  not,  describe  minutely 

an}'  variations. 


XLIX.     Miscellaneous  experiments.* 

a.   Schemer* s  experiment. 

(1 )  Prick  two  smooth  holes  in  a  card  at  a  distance  from 
each  other  less  than  the  diameter  of  the  pupil.  Fix 
two  long,  fine  needles  or  straws  in  two  pieces  of  wood 
or  cork.  Fix  the  cardboard  in  a  piece  of  wood  with  a 
groove  made  in  it  with  a  fine  saw,  and  see  that  the 
holes  are  horizontal.  Place  the  needles  in  line  with 
the  holes,  the  one  about  eight  inches,  the  other  about 
eighteen  inches  from  the  card. 

(2)  Close  one  eye,  and  with  the  other  look  through  the 
holes  at  the  near  needle,  which  will  be  seen  distinctly, 
while  the  far  needle  will  be  double,  both  images 
being  somewhat  dim. 

(3)  With  another  card,  while  accommodating  for  the 
near  needle,  close  the  right-hand  hole,  the  right-hand 
image  disappears;  and  if  the  left  hand  hole  be  closed, 
the  left-hand  image  disappears. 

(4)  Accommodate  for  the  far  needle,  the  near  needle 
appears  double.  Now  close  the  right-hand  hole,  and 
the  left  hand  image  disappears;  and  on  closing  the 
left-hand  hole,  the  right-hand  image  disappears. 
[Practical  Physiology — Stirling.] 

(5)  Explain  the  phenomena,  drawing  figures  which  show 
just  what  must  take  place  in  the  eye. 

*The  miscellaneous  experiments  of  Lesson  XLIX  have  been  taken 
from  Stirling's  Practical  Physiology.  The  author  takes  this  place  and 
opportunity  to  acknowledge  his  indebtedness  to  Prof    Stirling. 

222 


VISION.  223 

(b)  Pur kinje- Sanson's  images. 

(6)  In  a  dark  room,  light  a  candle  and  hold  it  to  one 
side  of  the  observed  eye  and  on  a  level  with  it.  Ask 
the  person  to  accommodate  for  a  distant  object,  and 
look  into  his  eye  from  the  side  opposite  to  the  candle, 
and  three  reflected  images  will  be  seen.  At  the 
margin  of  the  pupil,  and  superficially,  one  sees  a  small 
bright  erect  image  of  the  candle  flame  reflected  from 
the  anterior  surface  of  the  cornea.  In  the  middle  of 
the  pupil  there  is  a  second  less  brilliant  and  not 
sharply  defined  erect  image,  which,  of  all  the  three 
images,  appears  to  lie  most  posteriorly.  It  is  reflected 
from  the  anterior  surface  of  the  lens.  The  third  image 
lies  toward  the  opposite  margin  of  the  pupil,  is  the 
smallest  of  the  three,  and  is  a  sharp  inverted  image, 
from  the  posterior  surface  of  the  lens.  Ask  the  person 
to  accommodate  for  a  near  object,  and  observe  that 
the  pupil  contracts,  and  the  middle  image — that  from 
the  anterior  surface  of  the  lens — becomes  smaller  and 
comes  nearer  to  the  corneal  image.  This  shows  that 
the  anterior  surface  of  the  lens  undergoes  a  change  in 
its  curvature  during  accommodation. 

(7)  Place  in  a  convenient  position  on  a  table  a  large 
convex  lens,  supported  on  a  stand.  Standing  in  front 
of  it,  hold  a  watch  glass  in  the  left  hand  in  front  of 
the  lens  and  a  few  inches  from  it.  Move  a  lighted 
candle  at  the  side  of  this  arrangement,  and  observe 
the  three  images  described  above.  Substitute  a  con- 
vex lens  of  shorter  focus,  and  observe  how  the  images 
reflected  from  the  lens  become  smaller.  [Practical 
Physiology — Stirling.] 

(8)  Explain  the  phenomena,  using  drawings. 
c.    The  blind  spot. 

(0)  Marriotte's  experiment. — On  a  white  card  makea  black 


224  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

cross  and  a  circle  about  three  inches  apart.  Closing 
the  left  eye  hold  the  card  vertically  about  ten  inches 
from  the  right  eye  and  so  as  to  bring  the  cross  to  the 
right  side  of  the  circle.  Look  steadilyat  the  cross  with 
the  right  eye,  when  both  the  cross  and  the  circle  will 
be  seen.  Gradually  bring  the  card  toward  the  eye, 
keeping  the  axis  of  vision  fixed  on  the  cross.  At 
a  certain  distance  the  circle  will  disappear,  i.  c,  when- 
its  image  falls  on  the  entrance  of  the  optic  nerve.  On 
bringing  the  card  nearer,  the  circle  reappears,  the 
cross  of  course  being  visible  all  the  time. 
(10)   Map  out  the  blind  spot. 

Make  a  cross  on  the  center  of  a  sheet  of  white  paper 
and  place  it  on  a  table  about  ten  or  twelve  inches  from 
you.  Close  the  left  eye  and  look  steadily  at  the  cross 
with  the  right  eye.  Wrap  a  penholder  in  white  paper, 
leaving  only  the  tip  of  the  pen  point  projecting,  dip 
the  latter  in  ink,  or  dip  the  point  of  a  white  feather  in 
ink,  and  keeping  the  head  steady  and  the  axis  of  vision 
fixed,  place  the  pen  point  near  the  cross  and  gradu- 
ally move  it  to  the  right  until  the  black  becomes  in- 
visible. Mark  this  spot.  Carry  the  blackened  point 
still  further  outward  until  it  becomes  visible  again. 
Mark  this  outer  limit.  These  two  points  give  the 
outer  and  inner  limits  of  the  blind  spot.  Begin  again 
moving  the  pencil  first  in  an  upward  and  then  in  a 
downward  direction,  in  each  case  marking  where  the 
pencil  becomes  invisible.  If  this  be  done  in  several 
diameters  an  outline  of  the  blind  spot  is  obtained, 
even  little  prominences  showing  the  retinal  vessels 
being  indicated, 
ill)    To  calculate  the  size  of  the  blind  spot. 

Helmholtz  gives  the  following  formula  for  this  purpose: 
When  /  is  the  distance  of  the  eye  from  the  paper,  F 


VISION.  225 

the  distance  of  the  second  nodal  point  from  the  retina — 
usually  15  mm. — d  the  diameter  of  the  sketch  of   the 
blind  spot  drawn  on  the  paper,  and  D  the  correspond 
ing  size  of  the  blind  spot:     ~  =  —  or  D  =  Fj*. 

d.  The  macula  lutea  or  yellow  spot.      Maxwell's  experiment, 

(12)  Make  a  strong  solution  of  chrome  alum — filter  it, 
and  place  it  in  a  clear  glass  bottle  with  flat  sides.. 
Close  the  eyes  for  a  minute  or  so,  open  them,  and 
while  holding  the  chrome  alum  solution  between  one 
eye  and  a  white  cloud,  look  through  the  solution.  An 
oval  or  round  rose  spot  will  be  seen  in  the  otherwise 
green  field  of  vision.  The  pigment  in  the  yellow  spot 
absorbs  the  blue-green  rays,  hence  the  remaining 
rays  which  pass  through  the  chrome  alum  give  a  rose 
color. 

(13)  Is  it  possible  to  calculate  the  size  of  the  macula 
lutea  ? 

e.  Shadows  of  the  fovea  centralis  and  retinal  blood  vessels. 

Move,  with  a  circular  motion,  a  blackened  card  with 
a  pinhole  in  its  center,  in  front  of  one  eye  looking 
through  the  pinhole  at  a  white  cloud.  Soon  a  punc- 
tated field  appears  with  the  outlines  of  the  capillaries 
of  the  retina.  The  oval  shape  of  the  yellow  spot  is 
also  seen,  and  it  will  be  noticed  that  the  blood  vessels 
do  not  enter  the  fovea  centralis.  Move  the  card  ver- 
tically, when  the  horizontal  vessels  are  most  distinct. 
On  moving  it  horizontally,  the  vertical  ones  are  most 
distinct.  Some  observers  recommend  that  a  slip  of 
blue  glass  be  held  behind  the  hole  in  the  opaque  card, 
but  this  is  unnecessary. 


L.   Perimetry. 

In  the  foregoing  experiments  we  have  dealt  exclusively 
with  what  is  called  direct  vision,  i.  e.,  with  phenomena  in- 
volving the  formation  of  a  clearly  defined  image  upon  the 
macula  lutea.  Every  one  has  noticed  that  outside  the  range 
of  direct  vision  one  may  still  get  a  pretty  definite  idea  not 
only  of  form  but  of  color  as  well.  It  is  the  purpose  here 
to  ascertain  just  how  far  this  field  of  i?idirect  vision  extends 
in  every  direction  from  the  visual  axis;  or,  to  locate  the  peri 
meter  of  the  field  of  indirect  vision.  Various  instruments 
have  been  devised — called  perimeters  to  aid  one  in  peri- 
metry. 

All  of  these  appliances  have  for  their  object  the  map- 
ping of  the  field.  In  all  exact  methods  the  map  takes  the 
form  of  a  polar  map,  the  pole  corresponding  to  the  point 
where  the  line  of  vision  would  pierce  perpendicularly  the 
plane  of  the  map. 
/.  Appliances. — A  perimeter,  or  ruled  blackboard,  Fig.  32; 

perimeter  charts,  such  as  shown  in  Fig.  33. 
2.  Preparatio?i. — A  very    economical  and   exact   perimeter 
may  be  constructed  in  the  following  manner  : 

Take  a  blackboard  whose  dimensions  are  abont  1  m.  by 
1.5  m.  Locate  a  point  40  cm.  from  one  end  and  50  cm.  from 
either  side.  Let  this  be  the  point  of  fixation  or  the 
point  where  the  line  of  direct  vision  falls  upon  the  sur- 
face of  the  board. 

We  propose  now  to  draw  upon  the  board  a  series  of 
circles  whose  distance  from  one  another  shall  represent 
an  angular  distance  of  10°.      Reference  to  Fig.  31  makes 

226 


VISION. 


227 


it  evident  that  if  the  line  A  B  represent  the  plane  sur- 
face of  the  blackboard  and  if  the  eye  be  placed  at  O  the 
equal  increments  of  10°  on  the  quadrant  become  a  series 
of  increasing  increments  upon  the  surface  of  the 
board.  The  numbers  at  the  right  (Fig.  31)  show  just 
how  many  centimeters  the  radius  of  each  successive 
circle  should  be  provided  the  distance  of  the  eye  from 
the  board  be  taken  at  20  centimeters. 


Fig.  31. 

Fig.  31.    For  de 

scription  see 

L=2. 


Fig.  32.  Showing  method  of  ruling  a  black- 
board for  use  in  perimetry.  The  radii  of  the  cir- 
cles are  given  at  the  line    A  B  in  Fig.  31. 


After  drawing  the  circles,  draw  meridians  which  divide 
each  quadrant  into  three  to  nine  subdivisions.  The 
completed  blackboard  chart  will  have  the  appearance 
and    proportions    shown    in    Fig.    32.      The  circles  and 


228  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

meridians  should  be  traced  permanently  in  slate-colored 
enamel  upon  the  surface  of  the  blackboard.  Any  marks 
made  upon  the  board  with  chalk  may  then  be  erased 
without  disturbing  the  perimeter  circles. 

Make  test  objects  in  this  manner.  To  a  soft  pine  disc 
3  or  4  cm.  in  diameter  and  1  cm.  thick  fix  a  20  cm. 
handle  of  hard  wood.  The  whole  should  be  given  a  dead 
black  surface,  India  ink  is  good  for  this  purpose.  Upon 
the  disc  one  may  fix  with  a  pin  the  test  object  :  a  circle 
or  a  square  or  other  form  in  white,  yellow,  green,  blue 
or  red. 

Each  blackboard  chart  must  be  provided  with  a  rest 
or  contrivance  to  insure  that  the  subject's  eye  is  20  cm. 
from  the  surface  of  the  board.  Whether  this  takes  the 
form  of  a  rod  of  wood  extending  out  from  the  board  and 
so  adjusted  that  when  the  subject  rests  the  most  promi- 
nent infra-orbital  region  upon  its  end,  the  cornea  will  be 
20  cm.  from  the  center  of  the  chart;  or  whether  it  takes 
some  other  form  that  insures  the  same  result  is  of  little 
consequence. 
j.  Experiments  and  Observations. 

In  all  the  observations  which  are  subsequently  indi- 
cated, it  is  taken  for  granted  that  the  visual  axis  is  per- 
pendicular to  the  surface  of  the  chart,  that  the  center  of 
the  chart  is  the  point  of  fixation,  and  that  the  accommo- 
dation is  kept  uniform,  i.  e.,  the  eye  is  either  uniformly 
focused  on  the  pole  of  the  blackboard  perimeter  or  uni- 
formly relaxed;  further  that  the  eye  not  under  observation 
be  closed  or  closely  shaded. 

(1)  Examine  the  upper  median  quadrant  by  sweeping  a 
white  circle  or  square  around  arc.  G0°,  keeping  the  test 
object  as  near  the  surface  of  the  chart  as  possible.  If 
the  subject  does  not  see  it  at  all,  try  latitude  50°.  Hav- 
ing located  the  circle  which  seems  to  be  near  the  boun- 


VISION.  229 

dary,   locate    upon    each  meridian  a  point  which  indi 
cates  the  limit  of  indirect  vision  in  that  direction.    Join 
with  a  continuous  line  the  points  located,  thus  inclos 
ing  an  area  of  indirect  vision. 

(2)  Test  the  lower  median  quadrant  in  the  same  way. 
Is  the  total  area  covered  by  indirect  vision  in  this 
quadrant  greater  or  less  in  extent  than  that  in  the 
upper  quadrant  ? 

(3)  Test  the  upper-lateral  quadrant  and  then  the 
lower-lateral  quadrant.  Are  these  two  quadrants 
practically  equal  ? 

Is  there  any  ready  explanation  why  the  outer  two 
quadrants  should  contain  such  an  excess  of  area  over 
the  inner  two  quadrants  ? 

(4)  To  record  the  perimeter  outline. 

For  this  purpose  one  should  have  printed  charts  like 
the  one  given  in  Fig.  33.  Note  that  here  the  circles 
are  equidistant.  They  represent  concentric  arcs  of  a 
quadrant  with  10°  of  the  circle  between  each  two, 
while  the  circle  upon  the  blackboard-chart  represent 
a  radial  projection  of  these  arcs  upon  a  plane  tan- 
gent to  the  sphere  at  the  point  of  fixation. 

In  transcribing  the  perimeter  upon  the  record  chart 
one  has  only  to  locate  the  twelve  or  more  points  lo- 
cated upon  the  observation  chart  and  join  these  points 
into  a  continuous  perimeter. 

Point  x,  Fig.  30  for  example,  would  naturally  fall  at 
x'  Fig.  31;  point  y  corresponds  to  y';  Z  to  Z'  whose 
reading  is  :  "  Upper-lateral  quadrant  arc  64°,  70° 
from  vertical. 

(5)  In  the  above  experiment  we  have  determined  the 
perimeter  for  light  sensation  only;  the  subject  be- 
ing conscious  simply  of  a  light  or  white  spot  on  a  dark 
ground  but  not  certain  whether  the   spot  is  circular  or 


230 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


square.  Determine  now  the  form  perimeter,  i.  e.,  the 
limits  of  the  field  within  which  a  circle  can  be  defi- 
nitely differentiated  from  a  square  or  triangle. 

Chart    the  form-perimeter,  i.   e.,  transcribe  the  peri- 
meter upon  the  record   chart.      Is  it  similar  in  general 


Fig.  33. 

Fig.  33.     Perimeter  chart  foi    recording  the  limits  of  indirect  vision  for 
light,  for  color,  and  for  form. 

form  to  the  light  perimeter  ?  Is  it  much  smaller  in  area  ? 
Determine  and  chart  various  color-perimeters :  (a) 
yellow;  (b)  red;   (c)  green  and  (d)  blue. 


VISION.  231 

Have  the  color-perimeters  the  same  general  form 
as  the  Hg'ht-perimeter  ?  If  not,  describe  any  noticea- 
ble variations.  Which  of  the  color-perimeters  incloses 
the  greatest  area?  Enumerate  them  in  order  of  area. 
Is  this  the  order  which  one  would  expect  ?  Give 
grounds  for  position. 

(7)  Take  corresponding  perimeter  for  the  other  eye.  To 
use  the  same  blackboard  it  will  be  necessary  to  turn  it 
the  other  edge  up.  In  what  general  respect  do  the 
perimeters  of  the  right  eye  differ  from  those  of  the 
left? 

(8)  With  the  help  of  the  light  or  form-perimeters  of 
the  right  and  left  eyes,  determine  the  field  of  binocular 
vision.  Is  this  the  field  of  binocular  direct  vision  or 
binocular  indirect  vision  ? 


LI.   Determination  of  normal  vision,    a.   The  acuteness  of 

direct  vision,     b.  The  range  of  accommodation. 

c.  The  amplitude  of  convergence. 

a.  The  acuteness  of  direct  vision. 

/.  Appliances — Charts  printed  with  Snellen's  test  type; 
astigmatic  chart;  test  lenses  of  following  strength: 
+.50  D.,  +.15  D.,  +  1.00  D.,  +2.00  D.,  +  3.00  D., 
—  .50  D.,  —  .75  D.,  —  1.00  D.,  —  2  00  D.,  —  3.00  D ., 
+  1.00  D.  cyl.,  +  2.00  D.  cyl.,  —  1.00  D.  cyl.  —  2.  D. 
cyl.;  simple  test  frames,  and  shade;  a  photometer;  Holm- 
gren's worsteds. 
2.  Preparation. — Preparatory  to  testing  normal  vision  it  is 
necessary  to  make  a  few  general  statements  regarding: 
(1)    The  numeration  of  lenses. 

The  refractive  power  of  a  lens  is  the  reciprocal  of  its  focal 
distance.  The  refractive  power  of  a  lens  whose  focal 
distance  is  1  m.  is,  for  example,  only  one-half  as  great 
as  that  of  a  lens  whose  focal  distance  is  0.5  m.  Mon- 
oyer  introduced  the  term  dioptre  as  a  unit  in  measur- 
ing lenses.  One  dioptre — (1  D.) — represents  the 
refractive  power  of  a  lens  whose  focal  distance  is  1 
m.;  2  D.  corresponds  to  y2  m.;  3D.  to  ]A,  m.;  4  D.  to 
lA  m.,  etc.  0.5  D.  represents  the  refractive  power  of 
a  lens  of  2  m.  focal  distance;  0.25  D.  of  4  m.  focal 
distance,  and  0.125  D.  of  8  m.  focal  distance.  If  the 
lenses  are  convex  (bi-convex)  a  plus  sign  is  prefixed 
to  the  number,  i.  e.,  +  5  D.,  means  a  bi-convex  lens  of 
5  dioptres  refractive  power,  or  \  m.  focal  distance. 
While  —  5  D.  means  a  bi  concave  lens  of  \  m.  negative 
focal  distance. 

232 


VISION.  233 

The  use  of  cylindrical  lenses  is  frequently  necessary. 
A  cylindrical  lens  is  a  section  of  a  cylinder  parallel  to 
its  axis.  Cylindrical  lenses  may  be  convex  or  concave. 
A  convex  cylindrical  lens  capable  of  bringing  rays  to  a 
linear  focus  at  a  distance  of  one  half  meter  would  be 
designated  as  follows:  -f-  2  D.  cyl. 
(2)    Test  types  and  visual  angle. 

The  visual  angle  is  that  included  between  lines  joining 
the  extremities  of  an  object  and  the  nodal  point,  or  the 
angle  subtended  by  an  object,  at  the  nodal  point.  In 
Fig.  29  the  object  at  d  subtends  the  angle  v,  while 
the  object  at  D  though  much  larger  subtends  the  same 
angle  v.  Now  it  has  been  determined  by  Snellen  that 
the  normal  eye  distinguishes  letters  subtended  by  an 
angle  of  5  minutes.  If  we  let  d  =  distance  of  object 
from  nodal  point,  n  =  distance  of  image  from  nodal 
point,  i  length  of  image  and  o  of  object,  then: 

( 1 )  i  :  o  :  :  n  :  d ; 

(2)  o  =  -d; 

(3)  but-^=^  =  tan.  v; 

11  COS  V 

(4)  .  •.  o  =  d  tan.  v. 

The  tangent  of  5'  =  0. 001454;  assume  d  =  l  m  (1000 
mm.);  what  is  the  height  of  the  smallest  letter  dis- 
cernible to  the  average  normal  eye  at  that  distance? 

At  1  m.  height  of  letter,  o  =  0. 001454  X  1000=  1.45 
mm. 

Determine  the  height  of  the  letters  for  each  of  the 
following  distances  respectively:  60  m.,  30  m.,  20  m., 
15  m.,  12  m.,  9  m.,  6  m.,  4.5  m.,  3  m.,  2.5  m.,2  m.,  1.5 
m.,  1  m.,    0.75  m.,  0.50  m. 

What  is  the  size  of  the  image  in  all  these  cases? 
A  cultivation  of  the  visual  power  of  the  eye  may 
readilv  in   the  emmetropic  eye  bring  up  its  definition 


m  La  bora  tor  v  guide  in  phys/olog  y. 

to  }4  above  the  average  or  so  that  the  minimum  visual 
angle  for  acute  vision  equals  4'.  What  is  the  size  of 
the  image  when  it  subtends  an  angle  of  4'?  The  test 
letters  are  made  with  the  width  of  the  strokes  \  the 
height  of  the  letter.  What  is  the  width  of  the  retinal 
image  of  one  of  the  strokes?* 
j\    Experiments  and  Observations. 

(1)  To  test  the  form  sense,— In  all  of  the  tests  here  de- 
scribed it  is  understood  unless  otherwise  stated  that 
the  subject  sit  directly  facing  the  chart  which  should 
be  six  meters  distant,  and  well  illuminated. 

(1)  Let  the  subject  put  on  the  test  frames  with  the 
left  eye  shaded,  and  direct  the  right  eye  to  the  let- 
ters of  the  line  marked  6  m.  These  letters  in  their 
vertical  dimension  subtend  an  angle  of  5'.  The 
average  normal  eye  will  be  able  to  recognize 
easily  every  letter  in  the  line.  Should  there  be  any 
hesitation  in  the  differentiation  of  C  from  G,  of  P 
from  D  or  F,  of  K  from  X,  etc.,  make  a  note  of  it;  its 
significance  will  be  apparent  later. 

Now  in  recording  the  acuteness  of  vision  one  com- 
pares the  minimum  angle  of  distinct  vision  in  the 
subject  under  observation  with  the  normal.  If  the 
subject  reads  readily  at  6  m.  the  type  that  is  normal 
for  6  m.,  he  is  credited  with  normal  vision  or  with  a 
minimum  visual  angle  normal  or  unity.  This  is  ex- 
pressed in  the  following  manner:  Let  V  equal  visual 
acuteness;  d,  the  distance  from  chart;  D,  the  dis- 
tance at  which  the  type  should  be  read:  V  =  ^  .  In 
the   above   case  V  =  g-  or  1,  i.  e.,  normal  vision. 

(2)  Suppose   that   the   subject   cannot    read   the  f>   m- 

*  The   size  of  the  cones  of  the  macular  region  varies  from  0.0033 
to  0.003(5  mm.   in  diameter. 


VISION,  %\n 

line  readily,  let  him  try  the  line  above.  If  he 
reads  that  readily  his  visual  acuteness  would  be: 
V  =^-=^;  two-thirds  normal.  It  is  usual,  however, 
not  to  reduce  the  fraction  but  to  use  6  for  the  nume- 
rator always. 
(3)  How  shall  one  express  visual  acuteness  for  an  in- 
dividual who  reads  at  6  m.  what  he  should  read  at 
21m.?  At  24  m  ?  At  30  m.?  At  4.5  m.?  At  3  m.? 
\  |  How  many  members  of  the  class  have  a  visual 
acuteness  greater  than  unity?  May  a  visual  acute- 
ness above  the  normal  be  attributed  in  any  degree 
to  cultivation  of  the  vision,  or  is  it  to  be  interpreted 
solely  as  a  natural  endowment? 

(5)  Make  upon  a  white  card  with  india  ink  a  series  of 
vertical  lines  1  cm.  apart,  beginning  with  a  line  of 
1  mm.  breadth,  and  decreasing  gradually  to  a  hair 
line;  place  the  card  upon  a  blackboard  C  m.  distant; 
let  a  subject  with  high  visual  acuteness  say  how 
many  of  these  lines  he  can  see. 

With  dividers  and  rule  measure  the  breadth  of 
the  finest  of  the  lines  seen.  What  is  the  visual 
angle  of  that  breadth?  What  is  the  breadth  of  the 
retinal  image  of  the  line?  Can  the  subject  see  the 
same  number  of  lines  when  they  are  horizontal  ?  If 
not,  how  may  the  fact  be  accounted  for? 

(6)  If  it  be  found  that  the  subject  cannot  see  clearly 
the  largest  letters  upon  the  test  chart  let  him  move 
to  a  shorter  distance. 

Suppose  that  he  sees  clearly  the  30  m.  type  at  2 
meters,  what  is  the  value  of  V?  How  far  would  he 
be  able  to  read  the  6  m.  type?  At  what  distance 
would  he  probably  have  to  hold  a  book  whose  type 
has  a  height  of  1.8  mm.? 

(7)  {a)    Let    a    subject    take    the    seat,    6   m.  distant 


286  LAB  OR  A  7  OK  Y  G  UJDE  IN  PH  YSIOL  OGY. 

from  the  chart.  Hold  before  his  eye  a  -f-0.75  D. 
lens,  it  will  probably  make  indistinct  and  blurred 
distant  objects  which  were,  without  the  lens,  clear. 
If  such  be  the  case  it  is  likely  that  refraction  of  the 
eye  is  normal  and  for  our  purpose  it  may  be  re- 
corded as  an  emmetropic  eye. 

(6)  If,  however,  the  vision  remains  perfectly  clear 
for  distant  objects,  with  the  +0.75  D.  or  the  -flD. 
lens  before  the  eye  it  is  evident  that  the  refraction 
of  the  eye  is  not  normal. 
(<:)  Suppose,  on  the  other  hand,  that  distant  objects 
cannot  be  clearly  seen  with  the  unaided  eye;  but, 
with  the  help  of  concave  lenses,  clearly  seen,  it  is 
evident  again  that  the  refraction  of  the  eye  is  ab- 
normal. 

(8)  In  case  (7  c),  where  were  the  parallel  rays 
focused  when  the  concave  lens  was  used  ?  Where 
were  the  parallel  rays  focused  in  the  unaided  eye? 
Would  it  be  possible  for  the  condition  to  be  cor- 
rected by  an  exercise  of  the  accommodation?  If 
the  punctum  remotum  is  2  m.,  and  if  the  refractive 
indices  and  curvatures  of  the  refracting  surfaces  are 
all  normal,  in  what  way  must  the  eye  differ  from  the 
normal  eye  ?  This  condition  is  called  nearsighted- 
ness or  myopia. 

(9)  In  case  (7  fr),  if  a  subject  can  read  all  of  the  letters 
expected  of  the  normal  eye  one  credits  him  with 
V=4r;  but,  the  eye  may  have  accomplished  the  re- 
sult at  the  expense  of  more  or  less  effort. 

If  the  eye  have  a  punctum  remotum  beyond  infin- 
ity; /.  e. ,  if  the  rays  of  light  from  a  distant  object 
are  not  yet  converged  to  a  focus  by  the  time  they 
reach  the  retina  in  the  resting  eye  it  will  require  a 
certain  effort  of  accommodation  to  produce  a  clear 


J  'ISION.  237 

image.  Such  is  the  condition  in  the  farsighted  per- 
son, the  condition  is  called  hyperopia.  The  term 
farsightedness  does  not  mean  that  the  subject  can 
see  farther  than  the  average  individual  but  that  he 
can  see  far  more  easily  than  near.  If  a  subject  with 
V=g  can  see  as  clearly  or  more  clearly  when  the 
+0.75  D.  lens  is  in  front  of  the  eye  there  is  no 
reasonable  doubt  that  hyperopia  in  some  form  is 
present. 

(10)  Let  the  subject  direct  the  line  of  vision  toward 
the  center  of  the  chart  for  testing  astigmatism.  It  is 
probable  that  not  all  of  the  radiating  lines  will  appear 
equally  clear  cut  and  black,  for  most  persons  have  a 
small  degree  of  astigmatism.  If  the  lines  are  unequal- 
ly clear,  where  are  the  clearest  ones  located?  Do  they 
describe  a  diameter  across  the  circle  ?  If  so, 
describe  the  location  of  the  clear  diameter,  0° — 180° 
being  the  horizontal  diameter,  and  90° — 90°  the  verti- 
cal one. 

(11)  (a)  If  the  subject  has  normal  vision  with  no 
astigmatism  or  normal  vision  despite  a  slight  as- 
tigmatism, he  may  be  given  a  better  conception 
of  just  what  a  moderate  degree  of  astigmatism  is 
by  putting  a+  1  D.  cyl.  lens  before  his  eye;  or  a 
rather  high  degree  of  simple  astigmatism  by  try- 
ing   a    +  2  D.  cyl.  or   +  3  D.  cyl. 

(b)  How   may  the   subject  be   made  artificially  hy- 
peropic  ? 

(c)  How,  artificially  myopic  ? 
II.    To  test  the  light  sense. 

With  the  photometer  test  the  subject's  power  to  deter- 
mine the  difference  in  the  illumination  of  the  two  discs 
of  the  instrument. 


238  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

III.    To  test  the  color  sense. 

Let    the    subject    take    the    three    test    colors :     light 
green,   purple  and   red,   and  choose  from  the  mass  of 
worsteds  the  colors  which  he  considers   similar  ones, 
placing  the  chosen  color  in  the   class  to   which  it  be- 
longs.     It  is  not  difficult  to  determine  whether  or  not 
the  subject  has  a  normal  color  sense.     If,  for  example, 
he  is   red  blind 'he  will  not  see   the  red  in  the  purple, 
or  related  colors,  but  will  classify  these  with  the  blues, 
while  the  reds  will  be  confused  with  the  greens. 
b.  The     range     of     accommodation. —  The     amount     of 
refractive  change  induced  by  the  eye  in  adjusting  for  its 
punctum  proximum  after  it  has  been  at  rest,  i.  e.,  after  it 
has  been  adjusted  for  its  punctum   remotum,  is  termed 
the    range   of  accommodation.      In  a  previous    chapter 
the  punctum  proximum  and  punctum  remotum  were  deter- 
mined.     It  was  reserved   for  this   place   to   express  the 
position  of  these  limits  of    accommodation    in  terms  of 
dioptres,  and  thus  most  readily  determine  and  definitely 
express  the  range  in  simple    dioptres.      The  relation  of 
this  to  what  has  just  preceded  will  be  evident. 

Let  R  represent  the  distance  of  the  punctum  remotum 
from  the  eye,  then  the  refraction  at  rest  or  the  static  re- 
fraction r  equals   the  reciprocal  of   the  distance: 

Let  P  be  the  distance  of  the  punctum  proximum  from 
the  eye,  then  the  maximum  refraction  of  the  eye,  p 
equals  the  reciprocal  of  the  distance: 

(2)    P  =  ~- 
When  R  =  oo,  ~  —  0,  i.  e.,  static  refraction  equal  zero. 
When  P  —Vz  meter,  ~  =  8. 


VISION.  239 

Let  A  equal  the  range  of  accommodation;  Donders 
expressed  the  range  of  accommodation  thus: 

(4)  A=ig, 

Take  an  example:  Let  the  punctum  remotum  be  50 
cm.  {y2  m.)  from  the  eye,  the  punctum  proximum 
10  cm.  (y'y  m.);  substitute  the  distances  expressed  in 
meters  in  formula  (4)  and  one  obtains  A  =  \  m.  The 
range  of  accommodation,  i.e.,  the  accommodative  power 
of  the  eye  is  equal  to  a  lens  of  \  m.  focal  distance.  But 
a  lens  of  \  m.  focal  distance  is  an  8  dioptre  lens.  A  much 
simpler  way  of  arriving  at  this  result  is  to  use: 

r  (=  ^)  and  p  (  =-p).  If  we  let  a  =  ~,  then  we  may 
write: 

(5)  a  =  p  —  r. 

To  apply  this  formula  to  the  above  example  we  have 
a  =  10  D.  —  2  D.  =  8  D. 
,   Experiments  and  Observations. 

(1)  Determine  the   range  of    accommodation    for  each 
member  of  the  class. 

(a)  Determine  punctum  remotum  and  punctum  proxi- 
mum. 

(<£)   Record  these  quantities  in  meters. 

(V)  Substitute  these  values  in  formula  (5)  expressing 
the  distances  in  the  corresponding  dioptres,  i.  e., 
using  the  reciprocals  of  the  distances. 

(2)  Range  of  accommodation  in  myopia. 

{a)   Is  r  positive  or  negative  in  myopia  ? 

(b)  Is  a  always  less  than  p,  or  may  it  sometimes  be 
greater? 

(7)  What  is  the  average  range  of  accommodation  of 
the  myopes  of  the  class  ? 


240  LAB  OR  A  TOR  Y  G  VIDE  IN  PHYSIOLOG  Y. 

(3)  Range  of  accommodation  for  emmetropia. 
{a)   What  is  the  value  of  R  in  emmetropia? 
(/?)   What  is  the  value  of  r  in  emmetropia? 

(c)  What  is  the  relative  value  of  a  and  p  in  this  class 
of  cases  ? 

(d)  What  proportion  of  emmetropes  in  the  class? 

(/)   Have  they  all  the  same  range  of  accommodation  ? 

(/)  Can  any  probable  cause  be  assigned  for  any  varia- 
tions which  may  be  found? 

(g)  How  does  the  average  range  for  emmetropes  com- 
pare with  the  average  range  for  myopes  ? 

(4)  Range  of  accommodation  for  hyperopia. 

(«)  If  the  punctum  re?notum  is  "  beyond  infinity"  (!) 
that  is  equivalent  to  saying  that  the  eye  at  rest  does 
not  focus  parallel  lines  (from  infinity)  upon  the 
retina,  but  the  lines  must  be  more  than  parallel,  i.  e., 
from  beyond  infinity;  or,  better,  convergent;  but  if 
they  are  convergent  they  would  meet  behind  the 
cornea.  The  p.  r.  for  hyperopes  is  then  nega- 
tive in  direction  and  is  equal  to  the  distance, 
behind  the  cornea,  at  which  the  convergent  lines 
would  meet  if  prolonged.  It  follows  that  ^r-  is  in 
the  case  of  hyperopes  negative.  Our  formula  (3) 
would  then  take  the  form: 

v  °  )     A  P  ^        R  ^  P   ~    R 

Therefore,  formula  (5)  becomes  (5')  a  =  p  -f-  r. 
Now,  in  determining  r  one  may  use  a  convex  lens 
of  such  a  strength  as  to  give  the  rays  the  requisite 
convergence.  The  value  of  the  lens  in  dioptres  is, 
of  course,  the  value  of  r.  In  the  hyperope  a  is 
always  greater  than  p.  As  the  determination  of  the 
punctum  remotum  of  the  hyperopic  eye  is  a  matter 


VISION.  241 

for  the  clinician  to  deal  with,  we  will  omit  its  deter- 
mination here. 
(£)   If  a  member  of  the  class  wears  glasses  having  the 
following  formula  for  the  right  eye,  +'2D,  and  if  his 
punctum  proximum    is   12.5    cm.    distant  from   the 
cornea,  what  is  his  range  of  accommodation  ? 
(c)  What    is   the    range  of    accommodation  of    those 
hyperopes    in  the    class  whose    punctum    remotum 
may  be  determined  from  the  lenses  which  they  use? 
(</)   May  variations  in  range  be  accounted  for? 
(e)  Is  the  average  range  greater  or  less  than  that  for 
myopes  ?     For  emmetropes  ? 
(5)   Tabulate  the  values  of  p  and  of  r  for  the  class,  first, 
with  respect  to  age,  arranging  in  the  first  column  all 
of  the  cases  which  range  between  eighteen  and  twenty 
years,  in    the  second    column  twent)-one  to  twenty- 
three,  and  so  on.      Determine  the  average  for  p  and 
for  r  from  each  age  column. 
(#)   Does  age    within  the  limits  of  your  table  affect 

the  punctum  proximum  ?     If  so,  how  ? 
(^)   Does  age  affect  the  punctum   remotum  as  shown 

by  your  table  ? 
(c)   If  the  volume  of    data  justifies  it,  make  a  chart 
showing  the  effect  of  age  upon  the  range  of  accom- 
modation.     Use  the  age  units  for  divisions  of  the 
axis  of  abscissas,  and  dioptre  units  of  p  and   r  for 
the  divisions  of  the  axis  of  ordinates. 
c.  The  amplitude  of  convergence. — The  fact  of  the   con 
vergence  of  the  visual  axes  of  the  two  eyes  in  binocular 
vision  has  been  demonstrated  in  a  previous  lesson.      We 
come  now  to  the  measurement  of  this  function. 

To  measure  convergence. — To  get  a  clear  conception  of 
the  situation,  let  us  call  the  line  which  joins  the  centers 
of  rotation  of  the  eyes  the  base  line.     A  plane  perpen- 


242  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

dicular  to  the  middle  of  the  base  line  may  be  called  the 
median  plane.  Any  point  in  this  plane  which  is  fixed  by 
the  two  eyes  in  binocular  vision  may  be  called  the  point 
of  binocular  fixation.  The  line  joining  this  point  to  the 
middle  of  the  base  line  would  lie  in  the  median  plane, 
and  would  be  called  the  median  line. 

If  the  point  of  fixation  be  at  a  great  distance  (infinity) 
the  lines  of  fixation  of  the  two  eyes  would  be  parallel  to 
the  median  line.  In  this  case  there  would  be  no  con- 
vergence. If,  however,  the  point  of  fixation  be  near  there 
will  be  a  convergence  of  the  two  lines  of  fixation  toward 
that  point.  The  amount  of  convergence  is  greater  the 
nearer  the  point,  and  is  called  the  angle  of  convergence. 
The  angle  of  convergence  is  then  the  angle  between  the 
line  of  fixation  at  infinity  and  the  line  of  fixation  at  the 
given  distance  less  than  infinity,  the  given  distance  be- 
ing measured  on  the  median  line,  beginning  at  the  base 
line. 

The  geometric  situation  is  indicated  in  the  accom- 
panying figure  (Fig.  34).  Let  C  represent  the  center 
of  rotation  of  the  left  eye,  M  the  middle  of  the  base  line 
and  the  origin  of  the  median  line;  CP  the  line  of  fixa- 
tion of  an  object  at  infinity;  MM'  the  median  line;  the 
line  CM  is  one-half  the  base  line;  represent  the  distance 
CM  by  b.  The  angle  D'CP  is  the  angle  of  convergence 
when  D'  is  the  point  of  binocular  fixation.  As 
to  the  exact  measure  of  the  angle,  it  is  evident  from 
the  figure  that  the  line  MD',  which  we  may  represent  by 
d,  is  the  cotangent  of  the  angle  of  convergence  (ang.  c). 

The  unit  of  measurement  for  the  angle  of  convergence 
is  the  meter  angle  (Ma)  of  Nagel.  The  meter  angle  is 
the  angle  of  convergence  when  the  point  of  binocular 
fixation  is  1  m.  distant  (d  =  l,000  mm).  Ma  equals  the 
angle   whose    cotangent   is  '     (cot   Ma  =  'h).       The  aver- 


r/s/ox. 


243 


age  base  line  being  64  mm.,  the  average  Ma  may  be 
thus  expressed:  Cot  Ma  =  ^;  Ma=l°50'.  It  is  not 
customary  to  use  in  practice  the  absolute  values  for  the 
angles,  but  a  convenient  series  of  approximate  values 
suggested  by  Nagel. 

If  d  =  500mm.    {%  m.),   ang.  c  =  2   Ma;    if    d  =  ^j    m., 


Fig.  34. 

Fig.  34.    For  description 
see  LI=c. 


Fig.  35. 

Fig.  35.   For  description 
see  Ll-C=(5). 


ang.  c  =  3  Ma.  If  &~%  m.,  the  accommodation  =  4  I) 
and  angle  of  convergence  =  4  Ma. 

Besides  the  convenience  of  this  system,  it  indicates 
at  once  the  direct  relation  between  accommodation  and 
convergence. 

The  amplitude    of  convergence  is  the    total   number   of 


244  LABORATORY  GUIDE  J X  PHYSIOLOGY. 

meter-angles  of  convergence  which  the  individual  can 
call  into  play.  It  is  the  difference  between  the  punctum 
proximum  of  convergence  [pc]  and  the  punctum  re- 
motum  of  convergence  [rc]  expressed  in  meter  angles; 
which  are  really  the  reciprocals  of  the  distances.  This 
may  be  thus  expressed : 

f  1  )  —  =5- — h-  in  distances,  or; 
(2)   ac=pc — rc  in  meter  angles. 

Experiments   and  Observations. — Let    each    member   of   the 
class  be  in  turn  the  subject  of  examination. 

(1)  Determine  the  pupillary  distance,  i.  e.,  the  distance 
from  the  center  of  one  pupil  to  the  center  of  the  other 
when  the  eyes  are  fixed  on  a  distant  object.  One-half 
of  this  is  approximately  equal  to  b,  and  in  the  experi- 
ments which  follow  may  be  used  as  such. 

(2)  Take  a  board  1  m.  in  length  and  10  cm.  in  width. 
Along  the  middle  of  one  side  draw  a  line  which  may 
represent  the  median  line;  graduate  the  line  in 
decimeters;  the  proximal  )/?,  m.  may  be  graduated  in 
centimeters.  At  each  centimeter  or  decimeter  bore  a 
small  hole  into  which  a  post  may  be  set.  Make  two 
posts  about  5  cm.  or  10  cm,  in  height;  into  the  top  of 
one  set  a  needle,  split  the  top  of  the  other  so  that  it 
will  hold  a  card  printed  with  fine  type  (not  to  exceed 
1  mm.  in  height,  finer  if  possible).  Support  the 
board  so  that  it  shall  be  in  a  horizontal  plane  and 
5  cm.  or  10  cm.  below  the  eyes. 

(3)  To  determine  the  punctum  proximum  of  convergence: 
(a)  Let  the  subject  sit  so  that  the  line  on  the  board 
shall  be  in  the  median  plane  and  parallel  to  the 
median  line;  let  him  look  at  the  needle  when  the  post 
is  set  at  1  m.  Supposing  that  his  punctum  remotum 
is  at  infinity,  what  is  the  ang.  c? 


VJSIOA  245 

/'  Let  the  subject  look  in  turn  at  the  needle  when 
the  post  is  set  at  50  cm.;  at  40  cm.;  at  30  cm.;  at 
25  cm.;  at  20  cm.;  what  is  the  ang.  c  in  each  case, 
expressed  in  meter  angles  ? 

From  this  point  if  the  needle  appears  perfectly 
clearly  defined  move  the  post  up  toward  the  eyes 
1  cm.  at  a  time  as  long  as  the  vision  is  binocular 
and  the  image  single. 

As  soon  as  the  image   is  double  one  may  be  cer 
tain  that  the  eyes  are   no   longer  able  to   converge 
sufficiently  to  bring  the  images  upon  corresponding 
points  of   the  retina   and   that   the    punctum   proxi- 
mum  of    convergence  (pc)  has  been   passed.      Find 
the  nearest  point  at  which  the  image  is  single — the 
nearest  point  at  which  the  fine  printing   on   the  card 
is  perfectly  clear;   this  is  the  punctum  proximum  of 
convergence  (pc). 
(//)   Determine    the    punctum   proximum    of    conver 
gence  for  each  individual  in  the  class. 
(4)    To  determine  the  punctum  remotum  of  convergence  (rc). 
If    the    eyes   can    be    directed    parallel    but   cannot 
diverge,  the  punctum  remotum  may  be  expressed  as 
follows:      rc  =  1{=-^-=0.       Landoldt    says,  however, 
that  "  the  majority  of  normal    eyes  can  diverge  more 
or  less,"  i.e.,  there  is  a  negative  convergence  ( — rc). 

The  formula — (  2  ) .  .  .  ac  =  pc — rc  becomes 
ac  =  pc— ( — rc);  or 
2')...ae=pc+r° 

Let  it  be  noted  that  in  this  case  the  value  of  r* 
cannot  be  determined  by  carrying  the  object  to  a 
greater  distance,  but  recourse  must  be  had  to  abduct- 
ing prisms,  i.  e.,  prisms  whose  apices  are  turned  away 
from  the  median  line.      The  negative  convergence  may 


24fi  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

be  determined  by  finding  "  the  strongest  prisms  which 
a  person  can  overcome";  while  seeing  a  distant  object, 
without  double  vision.  The  deviation  of  a  prism  may 
be  taken  as  half  the  angle  of  the  prism;  a  No.  6  prism, 
produces  a  deviation  of  3°.  If  only  one  prism  be 
used  the  3°  is  divided  equally  between  the  two  eyes. 
Let  it  be  understood  that  two  prisms  of  equal  angle  be 
used. 

(5)  To  compute  the  ang.  c  in  meter- angles  for  any  prism  and 
any  length  of  base  line. 

Let  n  equal  the  angle  of  deviation,  i.  e.,  one-half  the 
number  of  the  prism.  Let  b  equal  one-half  the  base- 
line. Let  d  equal  the  distance  of  the  punctum  re- 
motum,    to    be  computed.     Then, 

(1)  b  :  d  :  :  sin  n  :  cos  n  (see  Fig.  35). 
(2)....d=  b.  ^LH  =  bcotn. 

^    J  sin  n 

But  the  punctum  remotum  of  convergence  (rc)  ex- 
pressed in  meter-angles,  is  found  by  dividing  lm.  by 
d,  therefore 

(3)....r«=-^°- 

^    J  b  cot  n 

If  a  person  whose  base-line  is  64  mm.  is  able  by 
divergence  to  overcome  a  pair  of  No.  6  prisms  his 
punctum  remotum  of  convergence  would  be  negative 
and  equal  to  1.63  Ma.  Determine  the  punctum  re- 
motum of  convergence  for  each  individual  in  the  class. 

(6)  Determine  the  amplitude  of  convergence  for  each 
member  of  the  class  using  the  formula;  ac=pc — rc. 
Tabulate  the  results. 

(7)  Compare  this  table  with  the  one  in  which  the  range 
of  accommodation  is  recorded.  Is  there  any  parallel- 
ism in  the  variations  of  accommodation  and  conver- 
gence ?  Does  age  seem  to  have  any  appreciable  influ- 
ence upon  the  amplitude  of  convergence  ? 


OPHTHALMOSCOPY    AND    SKIASCOPY. 
By  ALFRED  M.  HALL,  A.  M.,  M.  D. 


LII.     Normal  ophthalmoscopy,  direct  method. 

Gould  defines  ophthalmoscopy  as,  "  the  examination 
of  the  interior  of  the  eye  by  means  of  the  ophthalmoscope." 
Normal  ophthalmoscopy  is  the  examination,  by  means  of 
the  same  instrument,  of  the  normal  eye  or  a  model  of 
the  normal  eye. 

1.  Appliances. — An  ophthalmoscope,  with  concave  mirror; 
dark  room;  lamp;  and  Thorington's  skiascopic  eye  or  an 
equivalent. 

2.  Preparation. — Arrange  the  model  and  the  lamp  so  that 
they  will  be  in  the  horizontal  plane  with  the  observer's 
eye.  Place  the  skiascopic  eye  directly  in  front  of  the 
observer's  eye,  and  the  lamp  a  little  to  one  side  of  the 
model. 

3.  Operation. — Let  the  observer  hold  the  ophthalmoscope 
with  the  right  hand,  mirror  forward,  close  to  the  eye, 
directing  the  vision  through  the  hole  in  the  instrument. 
Throw  the  light,  reflected  by  the  mirror,  into  the  skia- 
scopic eye.  Find  the  red  reflection  of  the  fundus,  then 
gradually  lessen  the  distance  between  the  observer's  eye 

247 


24S  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

and    the    model    to    about    2  or  3   cm.    The    skiascopic 
eye  will    then   be   illuminated   and   the  fundus  with  its 
structures  will  be  clearly  defined. 
4.    Observations. 

a.  Adjust  the  model  to  represent  the  emmetropic  eye. 

(1)  Determine,  with  the  ophthalmoscope,  the  color  of 
the  fundus.     Enumerate  the  structures  seen. 

(2)  Describe  the  papilla,  or  entrance  of  the  optic 
nerve.  Is  the  papilla  in  the  visual  axis  or  to  one 
side  of  it?  Describe  its  position  with  respect  to 
the  visual  axis  of  the  eye  and  determine  the  most 
advantageous  position  of  observer,  model  and  in- 
strument to  get  a  direct  view  of  the  papilla  in  the 
right  eye;  in  the  left  eye. 

(3)  Describe  the  location  of  the  arteria  and  vena 
centralis  retina:  with  reference  to  the  papilla. 

(4)  The  ring  formed  by  the  border  of  the  papilla  is 
sometimes  called  the  scleral  ring  or  the  choroidal  ring. 
Can  this  ring  be  distinctly  seen  ? 

(5)  The  macula  lute  a  and  the  fovea  centralis  are  the 
most  sensitive  portions  of  the  retina  and  are  in  a 
direct  line  with  the  visual  axis  of  the  eye. 

What  is  the  most  advantageous  position  of  model, 
observer  and  instrument  in  order  to  get  a  direct  il 
lumination  of    this   part  of  the  fundus?     Describe 
the      appearance     of    the    structures     in    question. 

(6)  Describe  the  retinal  blood  vessels  minutely ; 
drawing  a  map  of  their  distribution. 

/>.    The  observation  of  the  retina  in  t'he  hyperopic  eye. 

Adjust  the    model   for   three  dioptrics   of    hyperopia. 

(7)  Are  the  retinal  blood  vessels  distinct  when  the 
above  described  method  of  observation  is  used? 

( 8 )  Place  in  the  rack,  before  the  model  eye,  the  follow 


VISION.  249 

ing  lenses,  with  each  one  testing  for  a  distinct  reti- 
nal image  : 

*±  1  D-»  ±  2  D->  ±  3  D->  and±  4  D- 
With    which     one    of     the    lenses    is    the     clearest 
image   obtained?     Are    all  of    the  images   of  equal 
size?     Explain,  giving  a  figure.* 

(9)  In  hyperopia  do  the  rays  focus  in  front  of,  on, 
or  behind  the  retina?  What  direction  do  the  rays 
take  after  leaving  the  hyperopic  eye  from  the  illu- 
minated retina?  Are  they  parallel,  divergent  or 
convergent  ? 

c.    Observation  of  the  retina  in  a  myopic  eye. 

Adjust    the    model  for    myopia,  e.  g.,  three  dioptrics. 

(10)  Are  the  retinal  blood  vessels  distinct  ? 

(11)  What  direction  do  the  rays  from  the  retina  take 
on  emerging  from  the  myopic  eye,  divergent,  con- 
vergent, or  parallel? 

(12)  In  which  of  these  three  cases  would  the  normal 
eye  be  able  to  get  a  clear  image  of  the  retinal  struc- 
tures ? 

(13)  In  which  case  would  a  correcting  lens  be  neces- 
sary? Should  one  use  a  convex  or  a  concave  lens; 
and  why  ? 


*In  all  work  with  the  ophthalmoscope  or  retinoscope  it  is  under- 
stood that  the  observer's  eye  is  emmetropic,  either  by  nature  or  by  cor- 
rection, and  that  his  accommodation  is  suspended.  One  may  get  a  clear 
view  of  the  retina  without  fulfilling  these  conditions,  but  one  cannot 
draw  reliable  optical  conclusions. 


LIU.     Normal  ophthalmoscopy,  indirect  method. 

/.  Appliances. — The  same  as  in  exercise  LII,  with  the  addi- 
tion of  a  lens  of  +  12  D.  to  +  20  D. 
2.  Operation. — With  the  model  or  eye  to  be  observed,  the 
light  and  the  observer  arranged  as  in  exercise  LII, 
direct  the  light  reflected  by  the  mirror  into  the  observed 
eye  and  find  the  red  reflection  of  the  fundus  of  the  eye. 
Hold  the  lens  between  the  thumb  and  index  finger  and 
place  it  directly  between  the  mirror  and  the  eye  under 
examination,  and  at  a  distance  from  the  latter  of  6-8  cm. 
Be  careful  that  the  center  of  the  lens  corresponds  to  the 
center  of  the  pupil  and  that  the  plane  of  the  lens  is  per- 
pendicular to  the  line  of  vision. 
j.    Observations. 

a.    Observation  of  the  emmetropic  eye. 

(\)  The  rays  of  light  emerging  from  the  observed  eye 
are  focused  by  the  convex  lens,  which  the  observer 
holds,  and  form  an  aerial  image  of  the  retina.  If 
a  -f-  12  D.  lens  be  used,  and  if  its  optical  center  be 
held  8  cm.  from  the  anterior  surface  of  the  cornea, 
how  far  from  the  cornea  will  the  aerial  image  be 
formed  ? 
(2)  Trace  in  the  image  all  of  the  structures  enumer- 
ated in  the  direct  method.  Is  the  image  erect  or 
inverted  ?  Is  the  field  larger  or  smaller  than  one 
sees  in  the  direct  method?  Are  the  structures  mag- 
nified or  the  reverse?  Account  for  all  phenomena, 
representing  the  optics  of  the  case  with  a  figure. 
(  3)  Does  a  change  in  the  distance  between  the  cornea 
of  the  model  or  eye  and  the  lens  which  the  observer 

250 


VISION.  251 

holds   alter  the    size    of    the    image  ?     Account  for 
observation. 

b.  Observation  of  the  hyperopic  eye. 
Adjust  the  model  for  3  D.  of  hyperopia. 

(4)  Does  an  increase  of  the  distance  of  the  lens  from 
the  cornea  cause  the  image  of  the  papilla  to  be 
altered  in  size?     Account  for  all  phenomena. 

c.  Observation  of  the  myopic  eye. 

Adjust  the  model  to  represent  3  D.  of  myopia. 

(5)  Does  the  increase  of  the  distance  of  the  lens  from 
the  eye  cause  the  image  of  the  papilla  to  become 
altered  in  size  or  reversed  in  position  ?  Account  for 
all  phenomena. 

(6)  If  the  position  of  the  +  12  D.  lens  which  the  ob- 
server holds  remain  the  same — 8  cm.  from  cornea — 
will  there  be  any  variation  in  the  distance  from  the 
cornea  of  the  retinal  image  for  the  hyperopic  eye 
and  myopic  eye  ? 

Will  the  distance  for  the  hyperopic  eye  be 
greater  or  less  than  for  the  emmetropic  eye  ?  Why  ? 
Will  the  distance  for  the  myopic  eye  be  greater  or 
less  than  for  the  emmetropic  eye  ?     Why  ? 

d.  Observation  of  the  human  eye. 

At  this  point  in  the  student's  work,  let  him  practice 
the  direct  and  indirect  method  of  ophthalmoscopy 
upon  his  comrades,  after  two  or  three  days  of  practice 
he  may  pass  to  the  following  exercise. 


LIV.     Skiascopy. 

Gould  defines  skiascopy  as  "  a  method  of  estimating 
the  refraction  of  the  eye  by  observation,  through  the 
ophthalmoscopic  mirror,  of  the  movements  of  the  retinal 
images  and  shadows."  Synonyms:  Fundus  reflex  test; 
umbrascopy;  pupiloscopy;  koroscopy;  keratoscopy;  ret- 
inoscopy,  etc. 

/.  Appliances. — A  simple  retinoscope  or  an  ophthalmos- 
cope with  a  plane  mirror;  Thorington's  skiascopic  eye 
or  an  equivalent;  dark  room;  lamp;  etc. 
2.  Operation. — The  observed  eye  and  lamp  are  to  have 
the  same  relative  position  as  in  ophthalmoscopy.  Let 
the  observer  sit  directly  in  front  with  the  eye  in  the 
same  horizontal  plane  with  the  lamp  and  observed  eye, 
and  somewhat  more  than  1  m.  distant  from  the  observed 
eye.  Throw  the  light  reflected  by  the  mirror  into  the 
observed  eye;  rotate  the  mirror  slowly  and  a  shadow  will 
be  seen  in  the  pupil  of  the  observed  eye. 
J.    Observations. 

a.  Observation  of  the  emmetropic  eye.      Adjust    the    model 
to  represent  emmetropia. 

( 1 )  Does  the  shadow  move  in  the  same  direction  as  the 
mirror  rotates  or  in  the  opposite  direction,  i.  e.,  does 
the  shadow  move  "with  the  mirror''''  or  "opposite?"" 

(2)  Is  the  movement  of  the  shadow  quick  or  slow. 

b.  Observation  of  the  myopic  eye. 

(I)  Adjust  the   model   to  represent  less   than  1  D.  of 
myopia. 
(3)   Note  that  the   shadow   movement    is  with    the 

252 


VISION.  253 

direction  of  the  mirror  rotation  and  that  it  is  rela- 
tively quick. 
(II)   Adjust   the  model  to  represent  a  myopia  of  more 
than  1  D. 

(4)  Note  that  the  shadow  movement  is  opposite  the 
direction  of  the  mirror  rotation  and  that  it  is  quick 
when  the  myopia  is  of  low  degree,  slow  when  of 
high  degree. 

(5)  Observe  alternately  the  three  conditions  indi- 
cated above  until  their  differences  are  so  familiar 
that  any  one  of  the  conditions  may  be  readily  and 
unerringly  detected  by  the  observer  when  they  are 
arranged  for  him  by  the  instructor. 

c.  Observation  of  the  hyperopic  eye. 

Adjust  the  model  to  represent  any  degree  of  hyper- 
opia. 

(6)  Note  that  for  a  low  degree  of  hyperopia  the 
shadow  movement  is  with  the  mirror  rotation  and 
quick. 

(7)  Note  that  for  higher  degrees  of  the  condition  the 
shadow  movement  is  with  the  mirror  and  slow. 

(8)  How  may  one  differentiate  a  high  degree  of 
myopia  from  a  high  degree  of  hyperopia  ? 

(9)  Is  there  any  difference  in  the  size,  shape,  dis- 
tance or  position  of  the  shadows  in  these  two  condi- 
tions ? 

d.  Observation  of  the  human  eye. 

Let  the  student  practice  upon  his  comrades. 

Note:  Observation  of  the  astigmatic  eye  is  inten- 
tionally omitted  here.  It  belongs  more  espcially  to  the 
clinical  phase  of  the  subject. 


PHYSIOLOGICAL    H/EMATOLOQY. 


Q.     PHYSIOLOGICAL  H/EMATOLOGY. 
By  W.  K.  Jaques,  Ph.  M.,  M.  D. 


INTRODUCTORY. 

The  scientific  world  is  constantly  giving  her  discoveries 
to  the  medical  profession  to  be  utilized  in  diagnosing  dis- 
ease and  in  providing  means  to  relieve  suffering.  Each  fact 
thus  obtained  is  a  step  nearer  to  the  goal  of  positive  medi- 
cine and  removes  us  farther  from  the  past  with  its  unsatis- 
factory theories  and  dogmas. 

Blood,  the  most  difficult  tissue  to  study,  has  at  last 
begun  to  give  up  its  secrets  to  the  patient  workers  in  phys- 
iological and  pathological  laboratories.  Although  the  facts 
are  few  compared  with  the  great  labor  it  has  taken  to  obtain 
them,  they  are  of  such  practical  value  that  no  practitioner 
can  afford  to  be  without  them. 

The  discovery  that  toxins  and  antitoxins  were  con- 
tained in  the  blood  serum  made  possible  the  production  of 
diphtheritic  antitoxin  and  gives  us  the  serum  diagnosis  of 
typhoid  fever,  beside  opening  a  wide  field  of  possibilities 
for  the  future. 

The  finding  of  the  plasmodia  of  malaria  is  often  of  the 
greatest  value  in  clearing  up  an  obscure  diagnosis.  When 
methods  sball  have  been  devised  which  will  make  their 
detection  less  difficult,  the  discovery  of  the  presence  of 
bacteria  in  the  blood  and  the  identification  of  the  same  will 
be  of  great  clinical  importance. 

257 


258  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

To  understand  the  appearance  of  pathological  blood,  a 
knowledge  of  normal  or  physiological  hasmatologyis  essen- 
tial. It  is  the  object  of  the  following  pages  to  assist  the 
student  in  obtaining  this  knowledge  and  in  laying  the 
foundation  for  the  study  of  pathological  haematology. 

A  knowledge  of  the  microscope  and  its  technique  is 
essential  and  the  work  of  the  student  should  be  so  arranged 
as  to  include  considerable  practice  with  that  instrument 
before  entering  upon  a  study  of  that  subject. 

If  the  practitioner  has  a  fair  knowledge  of  pathology, 
histology  and  bacteriology,  with  the  help  of  the  following 
suggestions  he  may  take  up  with  profit  the  subject  of 
haematology. 

In  class  work  the  blood  may  be  obtained  from  students. 
The  pain  is  minimized  if  the  blood  is  properly  obtained, 
and  practice  on  themselves  will  impress  this  fact  upon  the 
students.  The  general  practitioner  can  get  material  from 
his  patients. 

The  technique  of  haematology  can  only  be  acquired  by 
practice.  The  student  will  secure  this  more  readily  than 
the  practitioner  because  his  attention  will  not  be  dis- 
tracted by  diagnostic  possibilities.  It  is  well  for  the  prac- 
titioner to  go  over  the  whole  ground  several  times  for  the 
sole  purpose  of  mastering  every  detail.  Unless  the  tech- 
nical part  of  the  work  is  correctly  and  easily  done,  the 
specimens  will  be  unsatisfactory,  the  results  will  be  untrust- 
worthy and  the  knowledge  of  the  subject  imperfect. 

The  methods  here  employed  are  those  of  the  best 
students  of  haematology  with  modifications  from  the  ex- 
perience of  the  author.  Although  the  best  to-day,  to  mor- 
row they  may  be  remembered  only  as  the  stepping  stones 
to  more  perfect  work.  Many  truths  are  yet  undiscovered 
in  this  wonderful  river  of  life — the  blood — and  the  grati- 
tude of  a  race  will  be  due  him  who  reveals  them. 


LV.     Examination  of  fresh  blood. 

i.  Appliances. — Microscope;  one  twelfth  inchoil-immersion 
lens;  22  mm.  cover  glasses;  slides;  saddler's  needle  and 
holder;  clean  piece  of  old  muslin  one-half  meter  square; 
paper  and  pencil. 

2.  Preparation. — Clean  cover  glasses  and  slides  as  follows: 
Immerse  in  60%  acetic  acid,  then  wash  in  soap  and 
water  and  place  in  dilute  alcohol;  just  before  using, 
wipe  dry  and  place  under  a  bell-jar;  the  needle  should 
be  so  placed  in  the  holder  that  it  protrudes  one-fourth 
to  one-third  inch. 

A  convenient  needle-holder,  the  exact  size  of  which 
is  shown  in  Fig.  36,  may  be  obtained  from  a  dental  sup- 
ply house. 

if 


""^Uajl/w.'.  »■  /Id/,,  J — __ ._^) 


Fig.  36. 

A  medium  saddler's  needle  may  be  obtained  from  a  har- 
ness shop.  If  too  long,  it  can  be  broken  and  the  point 
used.  These  needles  have  three  cutting  edges  so  that 
blood  flows  easily  from  a  puncture  made  by  one. 
Operation. — Wipe  the  lobe  of  the  ear  with  a  damp 
cloth;  then  briskly  with  a  dry  cloth;  seize  the  lobe 
with  the  left  finger  and  thumb  quite  tightly;  thrust 
the  needle  into  the  ear  with  a  quick  stroke.  Wipe 
away  the  first  drop;  then  when  the  second  drop  has 
become  a  little  more  than  one  eighth  of  an  inch  across 
its  base,  bring  the  center  of  the  cover  glass  under 
the    drop    and     touch    the    lower    part  without    touch- 

259 


260  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

ing  the  ear  as  shown  in  Fig.  46.  Quickly  place  the 
cover  glass,  blood-side  down  on  a  clean  slide  and  exam- 
ine. 

4.  Precautions. — Cover  glasses  must  be  clean,  dry  and  free 
from  dust.  The  blood  must  be  collected  quickly  or  it 
will  form  rouleaux.  A  warm  stage  prolongs  the  normal 
appearance  of  the  blood.  Placing  the  microscope  in 
the  incubator  at  body  temperature  for  half  an  hour  before 
using  will  keep  the  slide  warm  for  some  time.  In  adjust- 
ing the  needle  for  puncture  the  condition  of  the  patient 
should  be  considered.  A  full  blooded  patient  will  require 
a  smaller  puncture  than  an  anaemic  one. 

5.  Observations. — Note  that  the  red  corpuscles  are  round 
in  shape.  As  the  plasma  dries,  it  causes  currents;  as 
the  corpuscles  float  in  these  they  strike  each  other,  dent, 
elongate  and  act  like  bags  of  jelly,  returning  to  their 
round  shape  when  free. 

a.  Red  corpuscles. 

(1)  Note  biconcavity;  what  causes  it  ? 

(2)  Are  there  variations  in  the  size  of  the  red  cells? 

(3)  What  is  crenation?     Note  when  it  begins. 

(4)  Do  you  see  two  motions  of  red  corpuscles?     De- 
scribe any  motion  seen. 

(5)  Do  you  see  small  motile  bodies  in  the  plasma? 

b.  White  corpuscles. 

(6)  How  do  white  corpuscles  differ  from  red  ? 

(7)  Do  they  float  as  easily  in  the  blood  current? 

(8)  How  do  they  compare  in  size  with  red  corpuscles  ? 

(9)  Why  are  white  corpuscles  smaller  in  fresh  blood 
than  in  dried  specimens  ? 

(10)  What  movements  do  you  see? 

(11)  Do  you  see  any  variation  in  size  ? 

(12)  In  which  kind  do   you  see  the  amoeboid   move- 
ments ? 


PHYSIOLOGICAL  H/EMATOLOG  Y 


>61 


(13)  Do  you   see   some  white   corpuscles   with   large 
granules  ? 

(14)  What  is  the  approximate  ratio  of  the  white  cells 
to  the  red  ? 


Fig    38a.     Thoma-ZfM>s  binod-corpuscle  counter. 


LVI.  Counting  red  corpuscles. 

1.  Appliances. — Microscope  with  one- seventh  inch  objec- 
tive, and  a  mechanical  stage;  needle  and  holder;  Thoma- 
Zeiss  counter. 

2.  Preparation. — (1)  The  counter  and  pipette  should  be  care- 
fully cleaned  with  water,  followed  by  alcohol  and  thor- 
oughly dried.  (2)  Prepare  the  following  solution  for 
diluting  blood  : 

Sod.  sulph gm.  107 

Aqua  dist c  c.  120 

j.  Operation. — Obtain  the  blood  as  described  in  Lesson  LV, 
allowing  it  to  collect  until  almost  ready  to  drop.  Then 
insert  point  of  pipette  into  the  drop  and  by  sucking  gently 
draw  the  blood  up  to  the  mark  0.5.  Wipe  the  end  of 
the  pipette  and  insert  it  into  the  diluting  solution,  sucking 
it  up  until  the  bulb  is  filled  to  the  mark  101.  Close 
ends  of  pipette  with  fingers,  rolling  and  shaking  it  about 
for  a  minute.  Blow  out  three  drops  of  the  diluted  blood. 
Then  drop  from  the  pipette  on  the  round  table  of  the  coun- 
ter just  enough  of  thedilution  tocover  it  when  the  coveris 
placed  upon  it  without  causing  any  of  the  liquid  to  flow 
over  into  the  moat.  (Fig.  38b).  Place  the  counting 
slide  under  the  microscope  and  find  the  upper  left  hand 
square;  count  all  the  corpuscles  in  it.  Then  count  the 
next  square  to  the  right  and  continue  until  all  the  upper 
row  has  been  counted;  write  down  the  number  of  cor- 
puscles. Then  move  the  counter  so  that  the  next  lower  row 
can  be  counted  from  right  to  left  continuing  until  all  the 
squares  are    counted.      Clean    the    counter;  agitate    the 

262 


/'// J  :s/(  1L0GH '  /  L  11. 1:  MA  TOLOG  Y.  263 

pipette,  blow  out  a  drop,  place  the  diluted  blood  on  the 
counter  and  count  as  before.  If  the  two  countings  are 
nearly  the  same,  this  will  be  sufficient;  if  there  is  much 
difference,  a  third  field  should  be  counted  and  an  aver- 
age taken  of  the  two  fields  nearest  alike.  Divide  the 
number  of  corpuscles  by  the  number  of  squares;  multiply 
this  by  200  to  make  up  for  the  dilution  and  then  by  400, 
because  each  square  is  equivalent  to  one  four-hundredth 
of  a  cubic  millimeter.  This  will  give  the  number  of  cor- 
puscles per  cubic  millimeter.      Count  the  corpuscles  on 


Fig.  38b. 

Fig.  38b.  Showing  the  right  and  the  wrong  way  to  fill  a  Zeiss  count- 
ing cell.  a.  Too  little  blood,  b.  Too  much  blood,  c.  The  proper 
amount  of  blood. 

one  half  the  boundary  of  each  square  but  do  not  count 
them  on  the  other  half. 
^.  Precautions. — See  that  the  blood  corpuscles  are  evenly 
scattered  over  the  field.  (Fig.  39).  If  they  are  clus 
tered,  it  shows  faulty  technique  and  the  counting  dilution 
must  be  prepared  again  with  more  care.  Clean  counter 
and  pipette  first  with  water  and  then  with  alcohol  after 
using,  being  careful  to  leave  the  tube  perfectly  dry.  The 
pipette  is  easily  broken.  Thefine  lineson  the  counter  are 
injured  by  rubbing  with  a  coarse  cloth.     The  cover  glass 


264 


LAB  OR  A  TOR  Y  G  UIDE  IN  PI  I  YSIOl.  OGY. 


should  be  adjusted   before   the  corpuscles   have   time  to 
settle. 
5.    Observations. 

(1)  Make  counts  of   red  blood   corpuscles  from  several 
apparently  normal  individuals. 

(2)  Is  there    any  appreciable  variation    in  the   number 
per  cubic  millimeter? 


o 

00 


Fig.  39. 

Fig.  39.     a.   Successful  blood  spread  with  corpuscles  evenly  distributed, 
b.   Poor  spread  with  corpuscles  clustered. 

(3)  Can    the  variation  be   attributed  to  faulty  methods  ? 

(4)  What  is  the  average  count  for  normal  individuals  ? 

(5)  What  is  the  range  between  maximum  and  minimum 
observations  on  the  normal  individuals  observed  ? 

(6)  Account,  if  possible,  for  the  variations  observed. 


LVII.  Counting  white  corpuscles. 

/.  Appliances. — Same  as  in  Lesson  LVI  with  the  substitu- 
tion of  the  large  bore  pipette. 

2.  Preparation. — Cut  a  square  out  of  a  circular  piece  of 
cardboard  which  fits  in  the  barrel  of  the  microscope 
with  mechanical  stage.  The  square  should  be  just  large 
enough  to  bound  the  counting  square  of  the  counting 
slide.  (Fig.  40).  Adjust  the  circular  card  with  the  square  in 


Fig.  40. 

Fig.  40.  Plan  of  cardboard 
diaphragm  for  microscope  tube. 
For  description  see  LV1I-2. 


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4 

it 

J 

*1 

21 

S 

IS 

6 

Fig.  41. 

Fig.  41.  Showing  the  sequence  of 
the  fields  counted.  For  description 
see  LVII  3 


it  in  the  upper  part  of  the  microscope  barrel  just  below  the 
eyepiece.      By    lengthening  and    shortening    the  micro- 
scope  the  square   can    be  adjusted  to  the  square  of  the 
counting  slide. 
(2)   For  a  diluting  solution,  use  the  following  : 

Acidum  acet c.  c.      4 

Aqua  dist c.  c.  100 

265 


266 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Operation. — Obtain  blood  as  described  in  exercise  LVI 
and  dilute  with  the  above  solution.  Bring  upper  line  of 
ruled  square  to  bottom  of  the  square  of  the  field;  then  the 
field  of  the  microscope  will  correspond  to  field  one  in  the 
figure.  Count  all  the  white  cells  in  the  field.  Then  fix 
the  eye  on  a  cell  in  the  upper  margin  and  bring  it  to  the 
lower  edge  of  the  field;  count  this  field  and  proceed  in  the 
same  way  to  field  3.  Turn  stage  back  to  ruled  space,  usT 
ing  the  border  to  indicate  where  to  begin  to  count.  Count 
fields  4,  5  and  6;  turn  back  to  ruled  square  and  proceed 


Fig.  42. 
Fig.  42.     Position  of  solution  tipped  to  receive  pipette  horizontally. 


to  1,  8,  9;  turn  back  to  ruled  square  and  count  10,  11  and 
12.  For  a  larger  count,  proceed  in  the  same  manner 
from  the  central  ruled  space  to  count  the  additional 
squares  enclosed  with  dotted  lines.  The  acetic  acid  in 
the  diluting  solution  renders  the  red  corpuscles  transpar- 
ent or  dissolves  them  entirely.  If  this  does  not  so  ap- 
pear, the  acid  is  too  weak  and  more  should  be  used  to 
obtain  the  desired  results. 
i.  Precautions. — Make  a  good  deep  puncture.  Have  a  large 
drop  of  blood.  Remember  that  the  bore  of  this  pipette 
is  larger  than  that  of  the  pipette  for  red  corpuscles  and 
the  solution  will  run  out  if  the  pipette  is  held  perpendic- 
ularly.    (Fig.  42.)    The  suction  also  must  be  more  gentle 


PHYSIOLOGICAL  LIsEMATOLOGY.  267 

than  with    the  small    bore  pipette.     Remember  to  thor- 
oughly clean  and  dry  the  pipette  after  using. 
Observations. 

(1)  Estimate  the  number  of  white  corpuscles  per  cubic 
millimeter  in  several  apparently  normal  individuals. 

(2)  What  is  the  proportion  of  white  to  red  corpuscles 
in  each  individual  ? 

(3)  Is  there  considerable  variation  in  number  of  white 
corpuscles  in  different  individuals? 

(4)  Is  there  considerable  variation  in  the  proportion  be- 
tween white  and  red  corpuscles  in  different  individ- 
uals? 

(5)  What  may  cause  the  variation  ? 


LVIII.  Counting  red  and  white  corpuscles. 

/.   Appliances. — Microscope    with    one-seventh    objective; 

needle    and    holder;    Thoma-Zeiss    counter    with    small 

lumened  pipette. 
2.  Preparation. — Prepare  the  following  solution  for  staining: 

toisson's  solution. 

Methyl  violet,  5  b 025  gm 

Sod.chlor 1.000  gm 

Sod.  sulph 8.000  gm 

Neutral  glycerin 30.000  cm 

Aqua   dist 160.000  cm 

J.  Operation. — Obtain  blood  as  described  above  and  dilute 
1  to  200  with  Toisson's  solution.  Place  the  counting  slide 
under  the  microscope  and  find  the  upper  left-hand  square; 
count  the  red  corpuscles  in  each  square  from  left  to 
right;  then  retrace  the  same  field  and  count  the  white 
corpuscles.  Repeat  this  procedure  with  the  next  row  of 
squares,  continuing  the  same  way  until  all  the  squares 
are  counted.  Write  the  number  of  red  corpuscles  on 
one  side  of  a  line,  the  white  on  the  other.  Clean  the 
counter;  agitate  the  pipette,  blow  out  a  drop,  place  the 
solution  on  the  counter  and  count  as  before.  If  there  is 
much  variation  between  the  number  of  first  and  second 
field,  count  a  third  field  and  take  the  average  of  the 
two  fields  nearest  alike.  Divide  the  total  number  of 
corpuscles  by  total  number  of  squares  counted;  multiply 
by  200  (amount  of  dilution)  and  then  by  400,  which  will 
give  number  of  corpuscles  per  cubic  millimeter.  The 
use  of  this  staining  fluid  enables  the  student  to  count 

268 


PHYSIOLOGICAL  HEMATOLOGY.  2G9 

both  red  and  white  corpuscles  at  the  same  time  instead 
of  counting  separately  as  in  Lessons  LVI  and  LVII.  This 
is  important  to  determine  the  relative  proportion  of  red 
to  white,  or  white  to  red  corpuscles. 

4.  Precautions. — Extra  care  must  be  exercised  in  cleaning 
pipette  after  the  use  of  this  staining  solution. 

3.    Observations 

(1)  Compare  the  results  of  this  method  with  those 
obtained  in  counting  red  and  white  corpuscles  separ- 
ately. 

(2)  Determine  the  proportion  of  white  to  red  corpuscles 
in  a  number  of  normal  individuals. 

(3)  Has  age  any  influence  on  the  proportion? 

(4)  Has  sex  any  influence  on  the  proportion? 

(5)  Has  the  general  condition  of  the  nutrition  any  in- 
fluence ? 

(6)  Is  the  proportion  always  the  same  in  one  individual  ? 
If  not,  is  there  any  periodicity  in  the  changes  ? 

(7)  Determine,  if  possible,  the  causes  of  the  variation. 


LIX.  Centrifugalizing  the  blood.    To  determine  the  rela= 
tive  volume  of  red  corpuscles  and  plasma. 

/.  Appliances. — Daland's  hematocrit  (Fig.  43);  small  rub- 
ber tubing  to  fit  capillary  tube;  needle  and  holder;  vase- 
lin;   white  paper. 

2.  Preparation. — Adjust  rubber  to  capillary  tube.  Put 
empty  tube  in  one  arm  of  crosspiece  to  preserve  bal- 
ance. 

j.  Operation. — Obtain  blood  from  the  lobe  of  the  ear  as 
heretofore  described.  Draw  capillary  tube  full  of  blood. 
Grease  the  finger  with  vaselin  and  hold  over  the  free 
end  of  the  tube  before  drawing  off  the  rubber.  Place  the 
tube  in  the  crosspiece  of  the  instrument  as  quickly  as 
possible  and  revolve  at  least  two  minutes  at  the  rate  of 
seventy  turns  per  minute.  Take  out  the  tube  and  lay 
on  a  piece  of  white  paper  to  read  the  divisions.  Each 
degree  of  the  scale  is  estimated  to  contain  about  100,000 
cells;  hence,  a  tube  in  which  the  red  column  stands  at 
50  would  indicate  about  5,000,000  red  corpuscles  per 
cubic  millimeter.  The  use  of  this  instrument  is  de- 
signed chiefly  to  show  the  volume  of  red  corpuscles  rather 
than  the  number,  as  shown  by  the  Thoma-Zeiss  counter. 

4.  Precautions. — See  that  the  instrument  is  securely  at- 
tached to  the  table  and  the  crosspiece  to  the  instru- 
ment before  setting  it  in  motion. 

5.  Observations  and  Problems. 

(1)  Determine  the  volume  per  cent  of   red   blood  cor- 
puscles in  a  number  of  normal  individuals. 

(2)  Do  apparently  normal  individuals  have  the  same  or 

270 


PI  I )  S/OLOCICAL  ILEM.l '/ X  >L OG  Y. 


271 


approximately  the  same  volume  per  cent  of  red  blood 
corpuscles.  If  not,  seek  for  causes  for  the  differences 
in  different  individuals. 


Fig.  43. 
Fig.  43.     Haemaiocrit. 


(3)   Does  the   same   individual    have  the  same  volume 
per  cent  of  red  blood  corpuscles  all  the  while  ? 


272  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

{a)   It   there  is  a  variation  is  there  any  periodicity  to 

be  observed  ? 
(/;)   Seek    for    causes    of    any    variations  in  the  same 

apparently  normal  individual. 

(4)  The  volume  per  cent  as  recorded  by  the  haematocrit 
varies  with  the  product  of  two  factors  ;  the  average 
volume  of  the  individual  corpuscles  multiplied  by  the 
number  of  corpuscles  per  unit  volume.  (V  oo  v  X  n) 
(<z)  Is  the  average  volume  of  the  individual  corpus- 
cles (v)  necessarily  constant? 

(£)  If  it  is  not  constant,  would  one  be  justified  in 
drawing  conclusions  regarding  the  number  of  cor- 
puscles per  unit  volume  (n)  after  observing  the 
volume  per  cent  (V)  with  the  haematocrit? 

(5)  What  variation  of  the  observation  as  above  made 
would  enable  one  to  determine  with  reasonable  accu- 
racy the   number  of  corpuscles  per  cubic  millimeter? 


LX.  Estimation  of  haemoglobin. 

1.  Appliances. — v.  Fleischl's  haemometer;  medicine  dropper; 
distilled  water;  needle  and  holder;  capillary  tube;  lamp. 

2.  Preparation. — See  that  the  capillary  tube  is  perfectly 
clean  and  dry;  if  there  is  any  doubt,  draw  a  thread  wet 
with  ether  and  alcohol  through  it.  Fill  one  side  of  the 
metallic  cell  about  one-quarter  full  of  distilled  water. 


Fig.  44. 
Fig.  44.      Fleischl's  Haemometer. 

J.  Operation. —  Puncture  the  ear  and  obtain  blood  drop. 
Just  touch  outside  of  drop  with  capillary  tube  held  in 
a  horizontal  position;  it  should  quickly  fill  by  capillary 
attraction.     Carefully  and  quickly  wipe  away  any  blood 

273 


274  LABOR  A  TOR  Y  GUIDE  IN  PHYSIOLOG  Y. 

that  may  be  on  the  outside  of  the  tube.  Plunge  it  into 
the  well  of  water,  shaking  it  back  and  forth  to  thor- 
oughly mix  the  blood  and  water.  With  the  medicine 
dropper  wash  the  tube  with  a  few  drops  of  distilled 
water;  then  remove  the  tube  and  draw  the  solution  in 
and  out  of  the  dropper  several  times  to  be  sure  it  is 
well  mixed.  Then  fill  both  compartments  to  the  brim 
with  the  dropper,  taking  care  that  the  mixture  of  blood 
and  water  shall  not  flow  over  into  the  pure  water.  Ex- 
clude daylight,  and  by  artificial  light  adjust  the  compart- 
ment containing  clear  water,  so  that  it  comes  over  the 
slip  of  colored  glass.  Adjust  the  reflector  so  that  light 
is  thrown  up  through  the  well.  Then  adjust  the  slip  of 
colored  glass  until  it  corresponds  with  the  color  of  the 
diluted  blood  and  read  the  amount  indicated  by  the 
scale.  This  will  give  the  percentage  of  haemoglobin, 
100  being  the  standard  for  normal  blood. 

Any  approximate  success  with  this  instrument  pre- 
supposes a  color  sense.  Even  when  this  is  present  in 
the  student,  the  instrument  itself  is  not  entirely  reliable 
as  there  is  sometimes  a  variation  in  the  colored  slips  of 
glass.  It  is  also  not  reliable  for  percentages  of  haemo- 
globin under  20. 
4.  Precautions. — The  capillary  tube  should  be  cleaned  by 
drawing  through  it  a  thread  wet  with  alcohol  and  ether. 
The  tube  must  be  filled  and  emptied  quickly  to  prevent 
coagulation.  In  reading  the  instrument,  do  not  face 
the  light  but  let  it  come  from  the  side.  The  instrument 
should  be  so  placed  that  the  wedge  will  not  move  from 
left  to  right  but  to  and  from  the  operator.  Use  as  little 
light  as  possible.  Use  first  one  eye  and  then  the  other. 
Move  the  screw  with  quick  turns  rather  than  a  gradual 
motion,  as  the  impression  of  a  glance  is  better  than  a 
prolonged  look. 


PHYSIOLOGICAL  JLEM  ITOLOGY. 

Observations  and  problems. 

(1 )  Determine  in  the  cases  of  several  normal  individuals 
whether  the  blood  is  normal  when  compared  with 
v.  Fleischl's  arbitrary  scale.  Let  the  same  observer 
make  two  or  three  consecutive  tests  of  the  blood  of 
each  subject.* 

Record  for  each  subject  the  average  of   the  two  or 
three  tests  made  by  one  observer. 

(2)  Account,  if  possible,  for  any  variations  found. 

(3)  Do   the    individuals  who    show  a   low  haemoglobin 
reading    show  also   a  low  volume   per  cent,  and  con 
versely  ?     If  so,  would  one  be  justified  in  the  conclu- 
sion that  the  haemoglobin  varies  as  the  volume  per  cent  of 
the  red  blood  corpuscles  ? 

(4)  Do  the  individuals  who  show  a  low  haemoglobin, 
reading,  show  also  a  smaller  number  of  red  blood  cor- 
puscles per  unit  volume,  and  conversely?  If  so,  would 
one  be  justified  in  the  conclusion  that  the  hcemoglobin 
varies  as  the  number  of  red  blood  corpuscles  per  unit  vol- 
ume? 

(5)  Are  there  any  conditions  in  which  both  of  these 
conclusions  may  be  consistent  with  the  results  of  the 
reasoning  at  the  end  of  the  previous  exercise,  LIX? 


*  If  the  same  observer  obtained  anproxim-uely  the  same  reading  on 
the  second  and  third  test  of  an  individual's  blood  it  may  be  taken  for 
granted  that  for  comparison  with  each  other  this  observer's  readings 
are  sufficiently  reliable. 


LXI.      i  iie    microscopic    technique    of    haematology.     a. 
Spreading  blood,     b.   Fixing  and  staining. 

a.  "Making  the  spread." 

/.  Appliances.  —  Microscope  with  one-seventh  objective; 
needle  and  holder;  square  cover  glass,  \  inch. 

2.  Preparation. — Clean  six  or  more  cover  glasses  with  di- 
lute acetic  acid,  soap  and  water,  and  alcohol. 

j.  Operation. — Puncture  the  ear  and  obtain  blood  as  de- 
scribed in  Lesson  LV.      Hold  a  cover  glass  in  each  hand 


Fig.  45. 
Fig.  45.     Showing  the  way  to  hold  the  cover  glasses. 

as  shown  in  Fig.  45.  With  the  one  held  in  the  left  hand 
just  touch  the  center  to  the  bottom  of  the  drop,  as  in 
Fig.  46,  being  careful  not  to  touch  the  ear.  Quickly 
place  upon  it  the  cover  glass  held  in  the  right  hand  as 
in  Fig.  47.  If  the  blood  is  fresh  and  the  glasses  clean, 
it  will  spread  rapidly  and  evenly  by  capillary  attraction. 
The  instant  it  stops  spreading  seize  the  upper  cover 
glass  with  the  right  hand  as  shown  in  Fig.  48,  and  pull 
it  quickly  apart  horizontally.        lace  the  cover  glasses, 

276 


PHYSIOLOGICAL  Il.KMA  LOLOGY. 


■Ill 


smeared  side  up,  to  dry.  When  dry,  examine  with  a 
one-seventh  objective.  It  requires  considerable  practice 
and  skill  to  make  a  good  spread,  although  the  operation 
seems  simple  enough.     In   a  good   spread,  the  red  cells 


'  s- 


Fig.  46. 
Fig.  46.     Touching  the  cover  glass  to  the  blood  drop. 


Fig.  47. 

Fig.  47.     Dropping   cover 

glass  upon  the  drop 

of  blood. 


Fig.  48. 

Fig.  48.     Showing  manner  of  holding  the 
cover  glass  to  jerk  them  apart. 


are  evenly  distributed,  as  in  Fig.  37.  In  a  poor  spread, 
the  cells  are  clustered,  and  new  spreads  should  be  made 
until  the  desired  result  is  obtained. 


218 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


p..  Precautions.  —  Care  must  be  taken  to  have  just  the 
proper  amount  of  blood;  too  little  will  not  spread  well 
and  too  much  makes  the  spread  too  thick  to  examine 
well.  The  blood  should  not  have  time  to  coagulate.  The 
cover  glass  should  not  touch  the  ear  in  obtaining  the 
blood.  The  blood  can  be  made  to  flow  again  after  it  has 
stopped  by  rubbing  the  ear  briskly  with  a  cloth. 

b.   Fixing  and  staining. 

/.   Appliances. — Cover  glasses;  solution  for  staining;  heater. 

2.  Preparation. — Clean  cover  glasses  carefully  with  soap 
and  water,  followed  by  alcohol.  Instead  of  a  copper 
plate  (Fig.  49)  or  oven  over  a  Bunsen  burner  usually 
used  in  laboratories,  a  heater  as  shown  in  Fig.  50  is  rec- 


Fig.  49. 

Fig.  49.     Common  copper  heat- 
ing plate. 


Fig.  50. 
Fig.  50.     The  water  fixing  plate. 


ommended.  Cover  glasses  should  be  dried  at  boiling 
point,  which  is  constantly  maintained  in  this  heater,  it 
being  filled  with  water  and  placed  over  a  burner.  There 
is  no  danger  of  scorching,  as  there  is  on  the  strip  of 
copper  over  the  Bunsen  burner.  With  the  pattern  and 
dimensions  given  in  Fig.  51,  any  tinsmith  can  quickly 
make  the  heater  out  of  copper. 

(2)   Prepare  the  following  solution  for  staining: 

Ebrlich-Bondi  powder  (Grubler) 1  gm. 

One-half  per  cent  sol.  acid  fuchsin 5  c  c. 

Aqua  dist 25  c.c. 

Let  this  solution  stand  one  week  and  filter. 


PHYSIOLOGICAL  IJ.EMA TOLOGY. 


279 


J.    Operation. 

(a)   Obtain  and  spread  blood  as  described  in  section  a. 

(<£)  Place  the  cover  glass,  spread  side  down  upon  the 
heater  and  maintain  at  100°C.  for  fifteen  minutes.  This 
process  dries  and  fixes  the  preparation. 

(V)  Remove  the  fixed  preparation;  cover  the  film  with 
staining  solution,  allowing  it  to  remain  from  six  to  ten 
minutes.  The  time  of  staining  depends  upon  the 
length  of  time  the  film  has  been  heated;  a  film  fixed 
quickly  will  stain  more  readily. 


Fig.  51. 
Fig.  51.     Plan  for  constructing  the  water  fixing  plate. 

(//)  Rinse  off  the  excess  of  stain  in  pure  water  and  dry. 
(e)   Mount  in  balsam. 

Precautions. — Be  sure  that  the  water  in  the  heater  is 
boiling  before  placing  the  films  upon  it.  Do  not  let 
the  water  boil  too  violently  or  it  may  boil  over  and 
spoil  the  films.  The  films  must  be  air  dried  before 
they  are  placed  upon  the  heater. 


LXII.  Differential  counting  of  white  cells  and  of  red  cells. 

/.  Appliances. — Microscope  with  one-twelfth  oil  immersion 
lens;  mechanical  stage  (not  essential  but  convenient). 

2.  Preparation. — Stain  as  in  Lesson  LXI.  Write  the  names 
of  varieties  of  cells,  which  may  become  familiar  to  the 
eye  by  the  study  of  the  colored  plate,  and  as  each  differ- 
ent cell  is  discovered,  record  that  fact  by  a  check. 
j.  Operation. — Begin  at  the  upper  left  corner  of  the  speci 
men  and  count  toward  the  right  the  different  cells  as 
they  come  into  view.  When  the  right  border  comes 
into  view  move  the  specimen  so  that  the  adjoining  lower 
field  is  brought  into  range  and  count  back  again.  Mark 
the  cells  found  under  their  proper  heads.  After  the 
observer  has  become  familiar  with  the  different  cells  he 
can  keep  in  mind  the  neutrophiles  for  the  entire 
trip  across  the  field,  but  the  others  he  had  best  mark  as 
soon  as  found. 

Varieties  of  leucocytes.     (Fig.  52  a.) 
Polymorphonuclear  neutrophiles.      (Neutrophiles.) 
Myelocytes, 
Small  lymphocytes, 
Large  lymphocytes, 
Eosinophiles, 
Eosinophilic  myelocytes. 

Varieties  of  red  cells.      (Fig.  52  b.) 
Normoblasts, 
Megaloblasts, 
Microblasts, 
Macrocytes, 
Microcytes, 
Poikilocytes, 
Polychromatiphilic  cells. 

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LXIII.  Study  of  bone  marrow. 

/.  Appliances. — Strong  vice;  five-eighths  inch  cover  glasses; 
microscope;  heater;  Ehrlich's  triple  stain  (See  Lesson 
LXI)  ;  section    of  bone  containing  red  marrow;  saw. 

2.  Preparation. — Clean  cover  glasses  as  usual  and  have 
water  in  heater  or  fixing-plate  boiling. 

J.  Operation. — Saw  a  transverse  section  of  bone  one  inch 
thick.  Place  it  in  the  vice  and  turn  the  handle  until  the 
bone  marrow  begins  to  ooze  out  on  the  surface.  Just 
touch  the  surface  of  this  with  one  of  the  cover  glasses 
and  proceed  exactly  as  in  exercise  LXI  a,  making  as 
good  a  blood  spread  as  possible.  Dry  smeared  side  up. 
Then  fix  and  stain  as  described  in  LXI  b.  Place  slide 
under  the  microscope  and  make  a  differential  count  of 
red  and  white  cells  as  in  LXII. 

4.  Precaution. — Have  the  bone  specimen  as  fresh  as  possi- 
ble. Saw  the  piece  to  be  used  just  before  putting  it  in 
the  vice  and  then  take  the  specimen  from  the  freshest 
side  of  the  bone. 

5.  Observations. 

(1)  What  cells  do  you  find  that  are  not  found  in  normal 
blood  ? 

(2)  Can  you  trace   these  cells   to    the  cells    of    normal 
blood  ? 


v£l 


PHARMACOLOGY. 


H.     AN  INTRODUCTION  TO  PHARHACOLOGY. 
By  H.  H.  Richter,  M.  D. 


INTRODUCTORY. 

While  the  following  experiments  will  more  forcibly  im- 
press the  student's  memory  with  the  action  of  the  drugs 
under  consideration  than  any  didactic  lecture  possibly 
could,  this  must  be  considered  as  of  secondary  importance. 
The  real  object  is  to  teach  pharmacological  technique- — to 
place  the  student  in  a  position  where  he  can  at  any  time 
in  the  future  demonstrate  experimentally  to  his  own  satis- 
faction the  activity  or  inactivity  of  any  drug,  and  its  modus 
operandi. 

With  this  object  in  view,  experiments  have  been 
chosen  which  can  readily  be  performed  by  the  student 
himself.  No  attempt  is  made  to  show  the  various  actions 
of  each  drug  used,  but,  instead,  the  most  conspicuous  and 
easily  demonstrated  action  of  each  is  utilized.  Considera- 
ble time  is  expended  on  the  reflex  arc,  because  the  action 
of  drugs  on  its  different  elements  is  most  readily  demon- 
strated. 

Little  can  be  found  concerning  the  doses  to  be  used  in 
experiments.  In  order  to  save  time  and  trouble,  the  dose 
to  be  used  in  each  of  the  following  experiments  is  given. 

285 


286  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

The  student  is  presumed  to  have  a  fair  working  knowl- 
edge of  the  technique  of  the  physiological  laboratory.  The 
use  of  the  myograph,  kymograph,  etc.,  the  setting  up  of 
electrical  apparatus,  such  as  batteries,  inductorium,  commu- 
tator keys,  and  the  use  and  effects  of  same.  As  to  the  litera- 
ture on  the  subject,  the  following  are  valuable,  and  have 
been  made  free  use  of: 

Smith's  translation  of  L.  Hermann's  "Experimental 
Pharmacology"  is  the  only  English  work  devoted  to 
technique;  Brunton,  "  Pharmacology,  Therapeutics  and 
Materia  Medica,"  and  "Pharmacology  and  Therapeutics;" 
White,  "Materia  Medica  and  Therapeutics;"  Stirling, 
"Practical  Physiology;"  Landois  and  Stirling,  "Text- 
book of  Human  Physiology."  These  comprise  most  of 
what    has    been  written  on  the  subject  in  English. 

Each  group  of  students  will  need  the  following  appar- 
atus and  material  for  the  experiments  : 
One  Daniell  cell ;  Dog  and  rabbit  holder  ; 

Inductorium;  Seeker;     Pins; 

Myograph;  Pin-pointed  pipette  ; 

Kymograph  ;  Fine  and  coarse  thread  ; 

Contact  key  ;  Normal  saline  solution  ; 

Two  frog  boards  and  stands;  Gutta-percha  tissue; 
Shielded  electrodes  ;  Chloroform  ; 

Physiological  operatingcase;  Ether  (common  sulphuric); 
Clippers  ;  Sulphate  of  morphin  ; 

Hypodermic  syringe  ;  Sulphate  of  atropin  ; 

Commercial  curare;  Sulphate  of  strychnin; 

Hydrochlorateof  pilocarpin;  Ticture  of   digitalis; 
Sulphate  of  veratrin  ;  Sodic  carbonate  ; 

Tincture  of  aconite  ;  Sodic  sulphate. 


LXIV.     Curare 

/.    Material. — One    dog;    2   frogs;    sodic   chloride;     curare. 

2.    Preparation. 

Prepare  following  solution  of  sodic  chloride,  0.0(5 
grms.  to  10  c.  c.  ;  curare,  0.1  grm.  to  10  c.  c.  Pith  frogs. 
Do  not  fasten  the  dog  to  the  board,  but  simply  restrain 
him.  Set  up  inductorium  and  myograph,  the  former  so 
as  to  obtain  single  induction  shocks. 

J.    Experiments  and  observations. 

(1)  Give  a  hypodermic   injection   of  0.02  grm.  curare  to 
the  dog. 

(a)  Record  the  condition  of  the  dog  just  before,  and 
every  ten  minutes  after  injections  of  curare  with 
special  reference  to: 

(I)  Muscular  activity. 

(II)  Respiration — number  and  depth. 

(III)  Circulation — rate    and    rhythm  of  heart-beat. 

(IV)  Which    stops    sooner,    respiration   or    circula- 
tion ? 

(b)  Formulate  the  total  effect  of  curare  upon  the 
animal. 

(2)  Ligate  the  thigh  of  a  frog,  except    the  sciatic  nerve, 
near  the  knee-joint. 

Inject    into   the  dorsal    lymph    space    0.0012  grms. 

curare. 

(#)  What  elements  enter  into  the  formation  of  a  "  re- 
flex arc  ?" 

(6)  What  motor  phenomena  would  result  from  in- 
creased irritability  of  any  part  of  the  reflex  arc  ? 

(r)   What    motor  phenomena  would  result   from  les- 

287 


8  LABOR  A  TOR  Y  G  UIDE  IN  PHYSIOL  OGY. 

sened  irritability  or  destruction  of  any  element  in 
the  reflex  arc  ? 

(//)  What  effect  has  the  ligature  of  the  thigh  on  the 
distribution  of  the  curare  ? 

(<?)  How  do  the  reflex  arcs,  of  which  the  gastrocnemii 
are  the  motor  ends,  differ  with  regard  to  the  distri- 
bution of  the  curare  ?  What  part  of  the  reflex  arc 
is  protected  from  curare  in  the   ligatured  limb  ? 

(/)  Describe  the  relative  reaction  of  the  gastrocnemii 
to  stimuli  (chemical,  mechanical,  electrical)  applied 
to  various  parts  of  the  body  and  limbs. 

(£■)  Is  the  sensorium  intact?  Is  it  reached  by  the 
curare  ? 

{A)   Is  the  cord  intact?     Is  it  reached  by  curare? 

(3)  Expose  the  sciatic  nerves,  near  the  body,  in  the  frog 
used  in  experiment  (2);  stimulate  them. 

(a)  What  elements  in  the  reflex  arc  enter  into  consid- 
eration in  this  experiment? 

(<£)  Which  of  these  elements  are  exposed  to,  which 
protected  from  the  poison  ? 

(c)  Are  both  sciatics  reached  by  curare? 

(d)  Is  there  a  difference  in  the  reaction  of  the  gas- 
trocnemii to  the  stimuli  applied  to  the  sciatic 
nerves? 

(e)  To  what  elements  of  the  reflex  arc  have  you  lim- 
ited the  possible  action  of  the  curare  ? 

(/)  Have  you  proven  that  curare  does  not  affect  the 
nerve  trunks  ? 

(4)  Expose  gastrocnemii  by  cutaneous  incision.      Stim- 
ulate the  muscles  directly. 

(a)  Is  there  a  difference  in  reaction  to  stimuli  ? 

(b)  If  a  muscle  in  a  poisoned  animal  reacts  to  direct 
stimuli,  but  not  to  indirect  stimuli,  though  the  nerve 
fibers  be  proven  to  be  intact,  on  what  element  in  the 
reflex  arc  must  the  poison  act? 


PHARMACOLOGY.  389 

(7)  Why  would  you  not  use  curare  as  an  anaesthetic 
if  the  poisoned  animal  does  not  react  to  painful 
stimuli  ? 

(5)  Make  two  muscle  nerve  preparations  as  described 
on  page  56.  Dip  the  nerve  of  one,  and  the  muscle  ol 
the  other  into  curare  solution.  The  parts  of  the 
preparations  not  immersed  should  be  kept  moist  with 
normal  saline  solution.  After  several  minutes  mount 
specimens  in  the  myograph.  Stimulate  the  nerves 
and  note  : 

{a)  The  relative  reaction  of  gastrocnemii  to  indirect 
stimulation. 

(fr)  Does  this  bear  a  resemblance  to  any  previous  ex- 
periment ? 

(V)  How  do  results  compare  with  those  of  previous 
experiment  ? 

(6)  Stimulate  the  same  muscles  directly, 
(a)   Relative  reaction? 

(6)   Taking   this  in  connection  with  preceding  experi- 
ment, where  have  you  proved  that  curare  acts? 
(c)   How  do   experiments    (5)    and  (6)   compare  with 
experiments  (3)  and  (4)  ? 
Note: — Failure  in  experiments  (5  )  and  (_6)  may  result 
from  insufficient  immersion  of  muscle  in  curare  solution, 
capillary  attraction  resulting    in  curare    reaching    muscle 
supposed  to  be  free  from  poison,   and  drying  of  parts  not 
immersed  in  solution.    Of  these  the  first  is  by  far  the  most  fre- 
quent cause  of  failure,  the  sheath  of  the  muscle  rendering 
the  absorption  of  poison  a  slow  process.      It  may  be  over- 
come by  making  a  few  slight  incisions  in  sheath,  or  inject- 
ing a  drop  of  the  curare  solution  directly  into  the  muscle. 
Failure  of  experiment   (2),   and   consequently  (3)   and 
(4),  may  result  from  ligature  around  thigh  being  not  tight 
enough  to  prevent  diffusion  of   curare  into  gastrocnemius. 


LXV.  Atropin. 

/.   Material. — 2    dogs;  atropin  sulphate;     morphin  sulph- 
ate; chloroform  (or  ether);  mask. 
2.   Preparation. — Make  up  following  solutions;   a  strong  so- 
lution of  atropin  0.4  grm.  to   10  c.  c.;  a  weak   solution, 
0.02    grams    to   10  c.  c;    morphin,  0.6   grams  to  10  c.  c. 
Simply  restrain  dog  "a."      Fasten  dog  "b"  to  board. 
Give    hypodermically,  0.03   grm.   morphin  to  dog   "  b," 
then  anaesthetize  him.      Set   up   induction  coil  so  as  to 
obtain  interrupted  current. 
J.  Experiments  and  Observations. 

(1)  Drop  three  drops  of  the  stronger  atropin  solution 
into  one  eye  of  dog  "  a,"  allowing  them  to  drop  in  at 
short  intervals,  and  obstructing  tear  duct  with  pressure 
of  finger. 

(a)  What  is  the  nerve  supply  of  the  iris  ? 
(/>)   On  what  local  elements  may  a  drug  act  to  produce 

alteration  in  size  of  pupil,  and  how  ? 
(7)   Would  a  drug,  acting    centrally,    though  applied 
to  one  eye,  be  likely  to  affect  one,  or  both  pupils  ? 

(d)  Would  a  drug,  acting  locally,  and  applied  to  one 
eye,  be  likely  to  affect  one,  or  both  pupils? 

(e)  Would  a  drug,  acting  locally  on  the  pupils,  but  in- 
jected into  the  circulation,  and  reaching  the  pupils 
in  this  way,  be  likely  to  act  on  one,  or  both  pupils  ? 

(/)   Are  either  or  both  pupils  affected  by  atropin,  and 

if  so,  what  effect  is  produced  ? 
(g)   Does   atropin    act    locally  or  centrally  to  produce 

its  effect  on  the  pupil  ? 

290 


PHARMACOLOGY.  291 

(Ji)  Can  you  devise  an  experiment  that  would  positively 
answer  question  "g."? 

(2)  Expose  the  vagus  of  dog  "b"  (see  pp.  110-111). 
Stimulate  it  with  weak  induced  current,  using  shielded 
electrodes. 

(a)   What  is  the  function  of  the  cardiac  fibers  of  the 

vagus? 
(i>)   How,  therefore,  would  you  expect  stimulation  of 

the    vagus    to    affect    rate  and  rhythm  of  the  heart 

beats  ? 
(V)   How   would  you  expect    severing  of  the  vagus   to 

affect  the  rate  and  rhythm  of  the  heart  beat  ? 
(d)   How  do  you  actually  find  the  rate  and  rhythm  of 

the  heart  beats  affected  by  stimulation  of  the  vagus? 

(3)  Count  the  pulse,  then  give  5  mgrm.  atropin  hypo- 
dermically. 

(a)  Count  the  pulse  at  short  intervals  after  the  injec- 
tion of  atropin  for  at  least  30  minutes,  or  until  its 
rate  is  markedly  affected. 

(£)  What  is  the  effect  of  atropin  on  the  rate  of  the 
pulse  ? 

(c)  Could  atropin  produce  this  effect  by  acting  on  the 
vagus  center?  On  the  vagus  fibers  ?  On  the  vagus 
terminations  in  the  heart?  On  the  heart  muscle 
direct  ? 

(4)  After  the  pulse  rate  has  been  markedly  affected  by 
atropin  stimulate  vagus  as  before,  using  shielded 
electrodes. 

O)   What  is  the  effect  on  the  rate  of  heart's  action? 

(6)  Compare  this  result  with  that  obtained  in  experi- 
ment (2). 

(<r)  Had  atropin  acted  solely  by  depressing  the  vagus 
center  would  we  have  found  a  difference  in  results 


292  LAB  OR  A  TOR  Y  G  UIDE  JN  PH  YSIOL  O  G  Y. 

in  stimulating  vagus  nerve   before   and   after  its  ex- 
hibition ? 

(d)  Had  atropin  acted  on  the  accelerator  apparatus 
would  there  be  a  difference  in  such  results  ? 

( e)  If  now,  on  stimulating  the  heart  muscle  directly, 
you  obtained  a  normal  physiological  effect,  to  what 
elements  have  you  limited  the  possible  action  of 
atropin? 

(/)   Basing  your  opinion  on  the  experiments  you  have 

performed,  to  what  elements  have  you  limited   the 

possible  action  of  atropin? 
(5)   Further  general  observations. 
{a)   Take  temperature  per  rectum. 
(£)   Note    condition    of    visible    mucous     membranes, 

with  regard  to  their  secretions. 
(c)   If  dog  can    be  kept  until  next   day,  note  size   of 

pupils. 


LXVI.     Pilocarpin. 

/.    Material. 

1  rabbit;  1  dog;  hydrochlorate  of  pilocarpin;  sulphate  of 
morphin;   sulphate  of  atropin;  chloroform. 

2.    Preparation. 

Make  solution  of  pilocarpin,  50  mgrms.  to  10  c.c;  atro- 
pin, 0.02  grm.  to  10  c.c. ;   morphin  0  6  to  10  c.c. 

Do  not  fasten   the   rabbit  to  the  holder.      Fasten  the 
dog  to  the  dog  board,  after  giving  preliminary  hypoder- 
mic injection  of  0.03  grms.  morphin. 
J.  Experiments  and  Observations. 

(1)  Give,    hypodermically,     0.02     grm.     pilocarpin    to 
the  rabbit. 

(a)    Record    symptoms    as    they    arise,    especially    as 
regards: 

(I)  Secretions; 

(II)  Pulse  rate; 

(III)  Size  of  pupil; 

(IV)  Temperature. 

(/>)   Formulate  the  total  effect  of  pilocarpin  upon  the 
animal. 

(2)  After  morphinizing  the  dog,  fasten   it  firmly  to  the 
dog-board  and  lightly  anaesthetize;  expose  both  vagi. 

Count  the  pulse.  Give  a  subcutaneous  injection  of 
0.03  grms.  pilocarpin.  After  salivation  has  become 
profuse  count  the  pulse  again. 

How  does  pilocarpin  affect  the  pulse  rate  ? 
Now  sever  the  vagi. 
(a)   How  does  the  severing  of  the  vagi   affect  the  nor- 
mal animal  ?    (See  page  100.  ) 

298 


294  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

{b~)  How  does  it  affect  an  animal  poisoned  by  pilocar- 
pin? 

(c)  Could  pilocarpin  alter  the  effect  produced  by 
severing  the  vagi  if  it  acted  on  the  proximal  side  of 
the  point  at  which  the  vagi  were  cut?  On  a  point 
beyond  that  at  which  they  were  cut? 

{d)  Could  the  pilocarpin  alter  the  effect  normally 
produced  by  severing  the  vagi,  by  acting  on  the 
cardiac  sympathetic? 

(<?)  Enumerate  the  possible  points  at  which  pilocar- 
pin may  act  to  produce  the  effects  observed. 

(4)  Give  to  the  same  dog  5  mgrms.    atropin,  hypoder- 
mically. 

(a)    Is  the  rate  of  heart-beat  altered  ? 
(£)   Where   does  atropin  act   to  produce   alteration  in 
rate  of  heart-beat  (see  atropin.) 

(c)  Does  atropin  antagonize  the  action  of  pilocarpin 
in  this  experiment? 

(d)  To  what  elements  have  you  limited  the  probable 
action  of  pilocarpin? 

(5)  General  observations. 

(a)  Compare  the  action  of  pilocarpin  with  that  of 
atropin,    throughout  the   range  of  action  observed. 

(b)  Is  atropin  a  physiological  antagonist  to  pilo- 
carpin ? 


LXVII.  Strychnin. 

Material. — One    dog;  two  frogs;  sulphate  of  strychnin. 

Preparation. — Make  a  solution  of  sulphate  of  strychnin 
0.01  gm.  to  10  c.  a;  also  concentrated  solution,  0.2  gm. 
to  10  c.  c.  Pith  frogs.  Do  not  fasten  the  dog  to  the 
dog-board.  Set  up  electrical  apparatus  toobtain  tetaniz- 
ing  current. 

Experiments  and  Observations. 

(1)  Hypodermic  injection  of   0.01  gm.  strychnin  to  the 
dog. 

(a)  Record  the  condition   before,    and    symptoms   as 
they  arise  after  exhibition  of  the    drug,  especially 

,   with  reference  to  : 

(I)  Muscular  activity.     Describe  convulsions. 

(II)  Respiration.      How   affected  by  reflexes. 

(III)  Circulation.     Rapidity  and  rhythm  of  heart. 

(IV)  If    death    occurs,    which    stops     sooner,    the 
circulation  or  respiration  ? 

(b)  Formulate  results. 

(2)  Ligate  thigh  of  frog,  except  sciatic  nerve,  at  junc- 
tion with  body.  Sever  all  structures  except  nerve 
and  femur,  just  below  ligature.  Separate  cut  surfaces 
with  rubber  tissue  to  prevent  diffusion  of  the  drug. 
Turn  the  frog  over  and  make  a  median  abdominal 
incision.  Pressing  viscera  aside,  pick  up  the  sacral 
plexus  of  nerves  going  to  the  uninjured  leg.  The 
sacral  plexus  may  be  readily  recognized,  lying  on  each 
side  of  the  median  line.  Pass  a  thread  loosely  around 
the  nerves,  so  as  to  quickly  find  them  when  wanted. 
Inject  into  dorsal  lymph  space,  0.0001  gm.  strychnin. 

295 


290  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

(a)  What  part  of  the  frog  is  reached  by  the  poison  ? 
What  part  protected  from  it?  Illustrate  by  diagram. 

(<£)  Were  strychnin  a  convulsant  through  its  action 
on  the  sensorium,  would  the  legs  be  equally  con- 
vulsed ?  If  it  acted  on  the  spinal  cord  ?  If  it  acted  on 
the  motor  nerves?  If  it  acted  on  the  muscles  directly? 

(r)   Are  both  legs  convulsed  ? 

(d)  To  what  parts  in  the  reflex  arc  have  you  limited 
the  action  of  the  strychnin  ? 

(3)  Using  as  a  guide  the  thread  formerly  passed  around 
it,  pick  up  sacral  plexus  and  sever  it  high  up. 

(a)  Does  the  strychnin  reach  the  motor  nerve  and 
muscles  of  uninjured  leg? 

(£)  If  strychnin  were  a  convulsant  through  its  action 
on  either  the  motor  nerves  or  the  muscles,  or  both, 
would  the  uninjured  leg  still  participate  in  the  con- 
vulsions ? 

{/)  Demonstrate  that  muscles,  sciatic  nerve  and  sacral 
plexus  below  the  point  at  which  it  was  severed,  are 
still  intact,  by  stimulating  distal  portion  of  latter. 

(</)  To  what  elements  of  the  reflex  arc  have  you  lim- 
ited the  possible  action  of  strychnin  ? 

(4)  Expose  the    heart  of  a  frog  and  ligate  the  aortas  at 
the  base.     Operation  as  follows  : 

Freely  expose  sternum  by  -f-  shaped  incision  and  laying  back  of 
flaps.  Remove  lower  half  of  sternum  with  scissors,  taking  care  not  to 
injure  vessel  in  abdominal  wall  which  comes  just  to  tip  of  sternum. 
Freely  incise  exposed  pericardium,  bringing  heart  into  view.  Grasp 
apex  of  heart  with  forceps,  taking  care  not  to  use  force  enough  to  cut 
through  ventricular  wall,  and  draw  heart  down  and  forward.  This  gives 
ready  access  to  bulbus  arteriosus  and  aortae.  With  an  aneurism  needle 
pass  fine  thread  around  latter,  taking  care  not  to  injure  auricles,  and 
ligate 

With  scalpel  cut  through  occipito-atlantoid  membrane,  from  side  to 
side,  and  bend  head  forward.      Remove  posterior  wall  of  upper  end  of 


P II ARM  A  CO  LOGY.  297 

spinal  canal  by  inserting  smaller  blade  of  strong  scissors  into  spinal  canal 
and  cutting,  taking  care  not  to  injure  cord.  Allow  a  drop  of  the  concen- 
trated solution  of  strychnin  to  fall  directly  upon  cord;  or  with  fine 
hypodermic  needle  inserted  1.5  cm  into  the  arachnoid  space  inject  two 
drops  of  the  solution. 

{a)  What  effect  has  ligation  of  the  aortae  on  the  cir- 
culation ? 

{F)  Would  stoppage  of  the  circulation  prevent  the 
drug  from  reaching  the  peripheral  terminations  or 
trunks  of  the  sensory  nerves?  Motor  nerves?  Muscles? 

(V)  Where  then,  must  strychnin  act  to  produce  the 
observed  symptoms  ? 

(d)  Would  cessation  of  the  circulation  delay  the  ac- 
tion of  strychnin  on  the  cord  by  slowing  the  rate  of 
its  absorption  by  the  latter? 

(5)  After  observing  results  in  experiment  (4),  destroy 
first  the  upper  then  the  lower  portion  of  the  cord,  by 
passing  a  wire  down  the  spinal  canal. 

(«)  How  does  destruction  of  the  upper  part  of  the 
cord  affect  the  convulsions  ? 

(b~)  What  is  the  result  of  the  destruction  of  the  en- 
tire cord  ? 

(r)  Do  the  results  agree  with  those  of  previous  ex- 
periments ? 

Note  : — Destruction  of  the  upper  part  of  the  cord 
during  the  preparation  of  the  animal  may  take 
place;  if  so,  the  upper  limbs  will  not  take  part  in 
the  convulsions. 

(6)  Further  observations  and  comparisons. 

(<?)  Compare  the  general  effects  of  strychnin  and 
curare  in  the  dog. 

(6)  Compare  results  obtained  in  experiments  consist- 
ing of  ligating  the  thigh  of  a  frog  except  the  sciatic 
nerve,  and  injecting,  in  the  one  case  strychnin,  in 
the  other  curare. 


LXVIII.     Veratrin. 

/.  Material. — Sulphate  of  veratrin;    1  dog;    3  frogs. 

2.  Preparation. 

Prepare  a  solution  of  veratrin,  50  mgrms.  to  10  c.c.  Pith 
frogs.  Restrain  dog,  but  do  not  fasten  to  board.  Set 
up  myograph  and  induction  coil,  the  latter  arranged 
for  single  induction  shocks. 

J.   Experiments  and  Observations. 

(1)  Give  a  subcutaneous  injection  of  15  mgrm.  veratrin 
to  the  dog. 

(a)   Describe  symptoms  as  they  arise. 
(£)   Summarize. 

(2)  Place  thread  around  the  sacral  plexus  of  the  pithed 
frog  so  as  to  easily  find  it,  as  described  under 
strychnin.  Inject  0.003  gms.  veratrin  into  dorsal  lymph 
space. 

(a)   Describe  symptoms  referable  to  rexflexes. 
(o)   Note  particularly  the  difference  between  a  forcible 
contraction  and  a  prolonged  contraction. 

(3)  Sever  the  sacral  plexus  around  which  the  thread 
has  been  passed. 

{a)  How  do  the  contractions  of  the  legs  in  response 
to  direct  stimuli  compare  ? 

(<£)  Has  severing  the  sacral  plexus  altered  the  dura- 
tion of  the  contraction  of  the  muscles  supplied? 

(V)  If  veratrin  still  produces  its  typical  effects,  to 
what  elements  in  the  reflex  arc  have  you  limited  its 
action  ? 

(d)  Compare  the  effect  of  severing  the  sacral  plexus 
in  a  frog  poisoned  with  veratrin  with  that  in  a  frog 
poisoned  with  strychnin. 

298 


PHA  RMA  COL  O  GY.  299 

(4)  Ligate  the  thigh  of  a  pithed  frog  at  the  junction 
with  the  body,  not  including  in  the  ligature  the  sciatic 
nerve.  Sever  all  tissues  just  below  the  ligature  ex- 
cept the  nerve  and  the  femur.  Carefully  separate 
the  cut  surfaces  with  rubber  tissue  so  as  to  prevent 
diffusion  of  the  drug.  Inject  0.003  gm.  veratrin  into 
the  dorsal  lymph  space. 

(a)  By  means  of  a  diagram  show  the  distribution  of 
the  poison. 

{b~)  Compare  the  contractions  of  the  legs,  noting  par- 
ticularly the  difference  in  the  duration  rather  than 
the  difference  in  the  force  of  the  contraction. 

(V)  If  the  protected  limb  reacts  normally  to  stimuli, 
to  what  elements  in  the  reflex  arc  have  you  limited 
the  possible  action  of  veratrin  ? 

(d)  Compare  results  with  similar  experiment  with 
strychnin. 

(5)  From  the  frog  used  in  experiment  (4)  make  two 
gastrocnemii  preparations.  Fasten  in  myograph  by 
means  of  femurs,  and  stimulate  them  directly,  making 
tracings  of  contractions. 

(a)    Compare  tracings. 

(6)   To  what  elements  have  we  limited  the  action  of 

veratrin  ? 
(Y)    Suggest    an    experiment  which    would    limit    the 

action  to  one  element. 

(6)  Very  cautiously  sniff  veratrin.  Describe  the  sensa- 
sation. 

(7)  General  observations  and  comparisons. 

(a)  Review  your  notes  on  the  action  of  curare,  strych- 
nin and  veratrin  upon  the  reflex  arc. 

(i>)  How  would  you  prove  that  a  drug  paralyzed  by 
its  action  on  the  spinal  cord? 

(r)  How  would  you  prove  that  a  drug  destroyed  reflex 
activity  by  its  action  on  some  part  of  the  sensorium? 


LXIX.  Digitalis. 

Material.  —  Tr.  digitalis  ;  sulphate  of  morphin  ;  sodic 
chloride;  chloroform;  two  dogs;  one  frog;  sodic  sul- 
phate (}4  sat.  sol.). 

Preparation.  —  Make  solution  of  morphin,  0.6  gm.  to 
10  c.  c.  Sodic  chloride,  0.06  gm.  to  10  c.  c.  Pith 
frog.  Morphinize  dogs,  using  0.03  gm.  and  chloroform 
them  previous  to  operation.  Set  up  induction  coil  so  as 
to  obtain  tetanizing  current,  having  contact  key  in 
primary  circuit.  Prepare  kymograph  for  tracing. 
Experiments  and  Observations. 

(1)  Fasten  a  dog  firmly  to  the  dog  board  and  lightly  an- 
aesthetize. Expose  the  vagus.  Count  the  pulse.  Using 
shielded  electrodes  and  separating  secondary  from 
primary  coil,  find  a  current  just  weak  enough  not  to 
affect  heart  when  applied  to  vagus.  Now  inject  0.0 
c.  c.  tr.  digitalis  subcutaneously.  After  waiting  at 
least  20  minutes,  in  the  meantime  using  no  anaesthetic 
except  a  repetition  of  the  morphin  if  necessary,  and 
keeping  the  wound  closed  after  moistening  with  saline 
solution,  stimulate  the  vagus  with  same  current  that 
before  the  exhibition  of  digitalis  was  unable  to  affect 
the  heart. 
(a)   What  is  the  function  of  the  cardiac  fibers  of  the 

vagus? 
(o)   What  result  is  produced    by    the    stimulation  of 
these  fibers  in  the  normal  animal? 

(c)  Does  digitalis  increase  or  decrease   the  excitably 
of  the  vagus? 

(d)  With  the  stimulus  applied  to  the  vagus  fibers  and 

300 


PHA  KM  A  CO  LOG  Y.  301 

the  cardiac  fibers  carrying  impulses  centrifugally, 
could  this  altered  excitability  be  due  to  central 
action  of  the  digitalis? 

(2)  After  morphinizing  dog,  fasten    firmly  to  dog  board 
and  lightly  anaesthetize;  expose  femoral  artery. 

Having  placed  mercury  in  the  manometer,  and 
filled  the  cannula,  connecting  tube  and  short  arm  of  the 
manometer  with  y2  saturated  sodic  sulphate  solu- 
tion, to  prevent  clotting,  insert  the  cannula  into  the 
femoral  artery,  in  a  direction  toward  the  heart.  There 
must  be  no  air  bubbles  in  the  apparatus  at  any  point. 
Let  the  float,  carrying  the  tracing  point,  rest  on  the 
mercury  in  the  long  arm  of  the  manometer  and  record 
on  the  revolving  drum. 

The  anaesthetic  should  be  discontinued  as  soon  as 
the  cannula  is  inserted  into  the  femoral  artery.  Take 
normal  tracing.  Now  give  the  dog0.6  c.  c.  tr.  digitalis 
hypodermically. 

{a)  Watch    effect    on    elevation  of  float,  making  trac- 
ings at  short  intervals. 
{b)   What  elements  enter  into  arterial  tension  ? 
(V)      How  does  a  "  high  tension  "   tracing  differ   from 

a  "  low  tenison  "  tracing  ? 
(</)      How    do    changes  in  tension  affect  the  elevation 

of  the  tracing  above  the  abscissa? 
(>)   What  effect  has  digitalis  on  arterial  tension  ? 

(3)  Having  firmly  fastened  a  pithed  frog  to  frog  board 
with  web  stretched  over  a  cover  glass  fastened  into  a 
hole  in  the  board  by  means  of  sealing  wax,  focus  the 
microscope  upon  a  certain  arteriole  in  the  field,  and 
measure  its  diameter  with  an  eyepiece  micrometer. 
Now  inject  into  dorsal  lymph  spaces  0.3  c.  c.  tr.  digi 
talis  and   measure  same   arteriole   at   intervals  of    10 


302  LABOR  A  TOR  Y  G  UIDE  IN  PHYSIO  LOG  Y. 

minutes.     Keep    the  web    moist    with    normal    saline 
solution. 

(a)  What  change  occurs  in  the  diameter  of  the  arteriole? 
(b~)   What  effect  would  you  expect  this  to   have  on  ar- 
terial pressure  ? 

(c)   Would  its  action  on  the  arterioles  help  to  account 
for  its  effect  on  arterial  pressure? 
(4)    Comparisons. — Compare   digitalis   and    atropin  with 
regard  to  (a)   their  effect  on  the  rate  of  the  heartbeat. 

(b)  Their  effect  on  the  irritability  of  the  vagus. 


LXX.     Aconite. 

/.  Material. — Tr.  aconite;    sulphate  of  atropin;    1   dog;    1 

frog;  sphygmograph. 
2.   Preparation. 

Make   solution  of   atropin,  0.02    grms.    to    10  c.c.      Pith 
frog.     Do  not  fasten  the  dog  to  the  dog  board. 
_?.    Experiments  and  Observations. 

(1)  Give  1  c.c.  tr.  aconite  hypodermically  to  the  dog. 
Record  symptoms  as  they  arise. 

(2)  Fasten  the  pithed  frog  on  its  back  to  the  board. 
Count  the  heart  beats,  exposing  heart,  if  necessary. 
Now  give  0.2  c.c.  tr.  aconite  subcutaneously.  What 
effect  has  aconite  on  the  pulse  rate  ?  (To  obtain  satis- 
factory results  observations  must  be  made  at  short 
intervals,  for  from  30  to  60  minutes.) 

(3)  After  the  pulse  has  been  markedly  affected,  inject 
into  the  dorsal  lymph  spaces  0.0002  grm.  atropin. 
Does  atropin  affect  the  pulse  rate  after  administration 
of  aconite? 

(4)  Take  a  sphygmographic  tracing,  of  the  radial 
pulse  of  a  student.  Note  the  pulse  rate.  Administer, 
by  mouth,  0.2  c.c.  tr.  aconite  and  0.06  c.c.  every  10 
minutes  until  action  on  pulse  is  noticeable.  Repeat 
tracing  and  counting  of  pulse  at  short  intervals. 

(a)  How  does  aconite  affect  blood  pressure  ? 

(b)  How  is  the  rate  of  the  heart's  action  affected? 
(V)   What  subjective  sensations  are  produced  ? 

(5)  Comparisons. — Compare  aconite  and  pilocarpin  with 
regard  to  their  action  on  the  gastrointestinal  system. 

303 


APPENDIX.    A. 


APPENDIX  A. 


i.    Normal  saline  solution. 

This  solution,  or  as  it  is  also  called   normal  salt  solu- 
tion or  physiological  salt  solution,  is  so  much  used  in  the 
physiological   laboratory  that  it  should  be  made  in  consid- 
erable quantity  and  always  easily  accessible. 
Formula: 

Common  salt  (C.  P.) 30  gms. 

Distilled  water 5  L. 

It  is  convenient  to  keep  the  solution  in  a  siphon  bottle. 
It  is  thus  protected  from  dust  and  evaporation,  and  is  al- 
ways easily  accessible.     See  Fig.  53. 


Fig.  53. 
Fig.  53.     Siphon-bottle  for  normal  saline  solution. 

2.     Frog  boards. 

There  is  probably  no  more   satisfactory  or  economical 
frog  board   than  a  piece  of  dressed  soft  pine  15  cm.  by  30 

307 


308  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

cm.,  and  one  or  two  centimeters  in  thickness.  Some  prefer 
to  use  cork  boards  which  come  in  pieces  10  cm.  by  25 
cm.  and  3^  cm.  in  thickness. 

3.     The  physiological  operating  case. 

A  convenient  case,  and  one  which  will  be  sufficient 
in  the  simple  experiments  presented  in  this  book,  contains 
the  following  instruments  : 

1   medium  scalpel, 

1   small  scalpel  with  narrow  blade, 

1   medium  scissors, 

1   microscopic  scissors, 

1   medium  dissecting  forceps, 

1  microscopic  forceps,  with  curved,  serrated  jaws, 

2  serre  fine  forceps,  with  stiff  spring  and  serrated  jaws, 
1   groove  director  and  aneurism  needle, 

1   silver  probe, 

1  blunt  needle,  for  pithing  frogs, 

2  dissecting  needles. 

The  case  may  be  of  leather  or  leatherette.  Such  a 
case  may  be  used  nearly  as  much  in  the  histological  as  in 
the  physiological  laboratory. 

4.     Galvanic  cells. 

For  general  use  in  the  physiological  laboratory  there 
is  probably  no  galvanic  element  superior  to  the  Daniell 
cell  (named  after  Prof.  J.  F.  Daniell,  of  King's  College, 
London).  Much  the  most  convenient  and  economical 
size  is  the  quart  or  liter  cell  whose  porous  cup  measures 
5-6  cm.  in  diameter  and  10  to  12  cm.  in  height.  If  more 
current  is  needed  than  is  furnished  by  one  of  these  cells  it 
is  very  easy  to  join  two  or  more  of  them  into  a  battery. 

In  large  laboratories  it  will  be  found  expedient  to  de- 
vote an  old  table  to  the  galvanic  cells.      This  table  should 


APPENDIX  A  309 

be  provided  with  a  supply  of  copper  sulphate  and  of  10% 
sulphuric  acid  in  large  siphon  bottles  similar  to  the  one 
suggested  for  normal  salt  solution  (Fig.  53),  except  that 
instead  of  the  short  tube  for  equalizing  pressure  one  may 
insert  a  filter  through  which  at  the  end  of  the  laboratory 
period  the  student  may  return  the  liquids. 

The  accumulation  of  zinc  sulphate  in  the  acid  makes 
the  renewal  of  the  acid  necessary  from  time  to  time.  The 
deposit  of  metallic  copper  upon  the  copper  plate  reduces 
the  copper  sulphate  solution  in  strength.  It  may  be  kept 
replenished  by  an  excess  of  crystals  of  that  salt  in  the  large 
supply  jar.  A  very  practical  method  of  amalgamating  the 
zinc  plates  is  to  have  a  jar  containing  10%  sulphuric  acid 
with  mercury  in  the  bottom;  as  the  plate  is  immersed  the 
acid  attacks  it  and  cleans  it  so  that  the  mercury  readily 
clings  to  it  and  may  be  rubbed  over  the  surface  with  a 
cloth.  Another  method,  which  is  preferred  by  some,  is  as 
follows:  Dissolve  *75  gms.  of  mercury  in  a  mixture  of  150 
c.  c.  strong  nitric  acid  and  300  c.c.  strong  hydrochloric 
acid.  Add  to  the  solution  450  c.c.  of  strong  hydrochloric 
acid.  Keep  this  amalgamating  solution  in  a  ground  glass 
stoppered  jar.  To  amalgamate  a  zinc  plate  one  need  only 
dip  it  for  a  few  moments  into  the  solution,  remove  it,  rinse 
under  the  spigot  and  rub  with  a  cloth. 

At  the  end  of  each  laboratory  period  the  cells  should 
be  emptied,  the  zinc  plates  rinsed  and  drained,  and  the 
porous  cups  left  in  a  tray  of  running  water,  or  at  least  in 
a  considerable  excess  of  water. 

5.     To  curarize  a  frog. 

In  experiments  on  the  irritability  of  muscle  tissue  it  is 
necessary  to,  in  some  way,  suspend  the  activity  of  the 
irritable  nerve  fibers  which  are  supplied  to  every  muscle. 
In  certain  other  experiments  it  may  be  advisable  to  thus 


310  LAB  OKA  TOR  Y  G  UIDE  IN  PH  YSIOL  OGY. 

remove  the  influence  of  the  nervous  system.  Curara — 
also  spelled  ctirare.  curari,  urari,  and  woorara,  woorari, 
wourali,  etc., — an  arrow  poison  used  by  the  South  Amer- 
ican aborigines,  is  the  means  usually  employed  to  accom- 
plish the  end  desired.  The  way  in  which  curare  exerts  its 
influence,  is  made  the  subject  of  study  in  another  place. 
Make  a  1%  solution  by  pulverizing  1  gramme  of  commer- 
cial curare,  and  dissolve  it  in  100  c.  c.  of  distilled  water. 
It  need  not  be  filtered  unless  intended  for  use  with  a 
hypodermic  syringe.  If  kept  in  a  ground  glass  stoppered 
bottle,  in  a  cool  place,  it  will  retain  its  efficiency  for 
months. 

The  most  convenient  method  of  curarizing  a  frog  is  to 
inject  with  a  narrow  pointed  pipette,  1-3  drops  of  the 
solution,  through  a  minute  ventral  cutaneous  incision. 

The  drug  will  begin  to  take  effect  in  a  few  minutes. 
The  maximum  effect  may  be  delayed  some  time. 

6.     To  prepare  the  kymograph  for  work. 

Remove  the  cylinder,  stretch  a  sheet  of  the  prepared 
glazed  paper  tightly  upon  the  surface,  place  it  upon  such 
a    stand   as  the  one  shown   in   Fig.   54;     set  the   drum    to 


Fig.  54. 
Fig.  54.     Drum  support  for  use  in  smoking  the  kymograph  drums. 

rotating  and  bring  the  triple  gas  flame  under  the  drum.    In 
a  few   moments   it  will   be   evenly   covered   with   a  film  of 


APPENDIX  A.  311 

carbon  which  is  as  sensitive  to  touch  as  a  photographer's 
plate  is  to  light. 

7.     A  fixing  fluid  for  carbon  tracings. 

Gum  damar 160  gms. 

Benzole  q.  s.  ad 2000  c.c. 

If  this  solution  be  kept  in  a  large  museum  jar  in  the 
laboratory,  the  removed  sheet  bearing  the  tracings  may  be 
dipped  in  toto  or  it  may  be  subdivided  and  dipped  in  sec- 
tions. Let  the  tracing  be  lowered  quickly  into  the  solu 
tion  and  after  a  few  seconds  taken  out  and  drained.  If  it 
be  now  laid  upon  a  sheet  of  filter  paper — or  a  newspaper — 
it  will  be  dry  in  a  few  minutes. 

8.     The  cardiograph. 

Any  laboratory  will  have  different  forms  of  cardio- 
graphs for  demonstration  purposes,  but  not  every  labora- 
tory is  able  to  afford  numerous  duplicates. 
An  expert  tinsmith  will  make  the  tam- 
bour pans  at  very  moderate  cost,  and  the 
student  can  do  all  the  rest.  Pans  may 
be  made  of  two  sizes  No.  1,  diameter 
FlG  55-  5  cm.,  depth  4  mm.,  outside  diameter   of 

tube  3  to  4  mm.,  length  of  tube  3  to  4  cm.  No.  2,  dia- 
meter 4  cm.,  depth  3  mm.,  tube  as  in  No.  1,  see  Fig.  55, 
To  make  the  cardiograph  : — Take  a  tambour  pan  No.  1, 
stretch  thin  sheet  rubber — the  dentists'  "rubber  dam,"  and 
sold  as  such  by  dealers — across  the  pan  and  tie  in  place 
with  thread.  A  few  drops  of  sealing  wax  will  keep  the 
thread  in  place  after  it  is  tied.  Mount  the  tambour  as 
follows  :  From  any  well  seasoned,  close-grained  hard- 
wood in  boards,  about  1  cm.  thick,  cut  small  triangular 
pieces  about  10  cm.  on  a  side.  In  the  center  of  each  tri- 
angle bore  a  hole  to  receive  a  medium  sized  cork  (about 


312  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

1.5  cm.  in  diameter)  the  upper  edges  of  the  triangle 
may  be  beveled  and  each  corner  may  be  furnished  with  a 
leg  by  screwing  into  each  corner  from  the  lower  surface, 
a  round  headed  screw,  leaving  about  1  cm.  of  the  screw 
out  to  serve  as  the  leg.  If  the  class  is  large,  the  demon- 
strators should  prepare  these  tambour  boards  in  advance. 
The  tambour  is  mounted  by  fitting  a  cork  to  the  hole 
in  the  tambour  board,  boring  the  cork  and  pressing  the 
tambour  tube  through  the 
hole  from  below  upward.  Fix 
a  button  of  cork  to  the  mem 
brane  with  sealing  wax.     The 

completed     cardiograph    will 

V  .  ,  ,  Fig.  56. 

present  in  section  the  rela- 
tions shown  in  Fig.  56.  As  will  be  seen  from  the  cut, 
the  position  of  the  button  may  be  varied  by  varying  its 
shape  or  by  changing  the  adjustment  of  the  tambour  tube 
in  the  cork.  The  cardiograph  tambour  is  the  receiving 
tambour. 

o.     Tambours. 

It  is  probable  that  no  part  of  the  laboratory  equipment 
is  more  in  use  than  the  various  forms  and  adjustments  of 
the  tambour.  The  possibilities  of  this  device  were  first 
brought  out  and  developed  by  Marey,  Director  of  the 
Physiological  Institute  of  the  Ecole  des  Hautes  Etudes 
en  Sorboune,  Paris. 

If  the  laboratory  cannot  afford  to  furnish  at  least  one 
pair  of  the  Marey  tambours  to  each  table,  recourse  may 
be  had  to  such  a  device  as  that  just  described  above  under 
the  cardiograph.  Such  simple  tambours  when  carefully 
constructed  prove  most  satisfactory. 

To  construct  a  recording  tambour  :  Use  a  No.  2  tambour 
pan,  stretch  the  rubber  less  tightly  than  for  the  receiving 


APPENDIX  A.  313 

tambour  and  mount  similarly  in  a  triangular  tambour 
board,  omitting  the  screw  legs.  Make  a  recording  needle 
like  the  frog's  heart  lever,  except  that  the  foot,  which  rests 
upon  the  middle  of  the  tambour  membrane,  should  pre- 
sent a  larger  surface.  The  cork  which  forms  the  fulcrum 
of  the  lever  should  be  fixed  to  the  tambour  board  in  such 
a  position  that  the  long  arm  of  the  lever  is  vertically  above 
a  diameter  of  the  tambour.  Any  change  of  pressure  upon 
the  air  in  the  tambour  will  cause  the  membrane  to  rise  or 
fall,  thus  producing  in  the  tracing  point  of  the  lever  a  cor- 
responding rise  or  fall,  differing  from  that  of  the  membrane 
only  in  its  greater  extent.  It  is  evident  that  if  the  tube  of 
the  receiving  tambour  be  joined  to  the  tube  of  the  record- 
ing tambour  through  a  thick  rubber  tube  any  movements 
which  affect  the  button  of  the  first  will  be  manifested  by  a 
rise  or  fall  of  the  lever  which  rests  upon  the  second. 

10.  The  stethograph. 

In  order  to  record  graphically  the  movements  of  the 
chest  one  may  use  various  mechanical  devices.  The  most 
simple  device,  and  a  most  effective  apparatus,  when  only 
the  time  relations  and  the  character  of  the  movements  are 
matters  of  concern,  is  the  instrument  which  involves  the  use 
of  two  tambours,  a  receiving  and  a  recording  tambour. 
The  latter  is  the  one  describedab  ove,  (9.) 

A  receiving  tambour  may  be  constructed  especially  for 
this  purpose  as  follows  :  Let  a  tinsmith  construct,  from 
small  brass  wire,  {J/2 — ^  mm.  in  diameter),  spiral  springs 
which  shall  present  the  outline  of  truncated  cones  (See 
Fig.  57  a),  and  fit  inside  the  larger  tambour  pans. 

If  the  student  be  supplied  with  tambour  pans,  spring, 
"rubber  dam,"  thread,  sealing  wax  and  cork,  he  may  con- 
struct his  receiving  tambour    by   placing   the  spring  in  the 


314 


LABORATORY  GUIDE  IAr  PHYSIOLOGY. 


tambour  pan,  stretching  the  sheet  rubber 
over  the  spring,  tying  and  sealing.  The 
now  conical  diaphragm  of  the  receiving 
tambour  should  be  provided  with  a  cork 
button,  and  adjusted  by  passing  its  tube 
through  a  horizontal  hole  near  the  end  of 
one  of  the  wooden  rods  (see  Fig.  18). 
Connect  the  tambours  by   means  of  a  small  rubber  tube. 


Fig   57. 


ii.  The  thoracometer. 

If  one  wishes  to  measure  the  extent  of  the  movements 
of   the   thoracic    walls   the    stethograph,    for    mechanical 


Fig.  58. 

Fig.  58.     Receiving  button  for  Thoracometer — an  instrument  for  use  in 

quantitative  determination  of  variations  in  thoracic  diameters. 

reasons  too  apparent  to  need  enumeration  here,  affords,  in 
the  height  of  the  recorded  waves,  unreliable  data.  To 
make  a  quantitative  determination  of  the  variation  of  any 
diameter  of  the  thorax  requires  the  application  of  a  differ- 
ent principle.  The  following  method  has  been  success- 
fully used:  Construct  the  apparatus  shown  in  the  accom- 
panying cut,  using  for  the  spiral  spring  brass  wire  1.5  to  2 
mm.  in  diameter.  The  cone  defined  by  the  spring  should 
be  6  or  7  cm.  across  the  base  and  should  have  an  altitude 
from  the  base  to  the  contact  surface  of  the   hard   rubber 


APPENDIX  A. 


315 


button  of  about  4  or  5  cm.  It  may  be  fixed  to  the  hard 
wood  or  fiber  base  with  three  staples  and  the  base  in  turn 
fixed,  as  indicated  in  the  figure,  to  an  iron  rod  about  1  cm. 
thick  by  30  cm.  long.  A  hole  is  bored  through  the  base  in 
the  middle  of  the  cone.  A  pulley  whose  plan  and  elevation 
are  given  in  Fig.  58  b  and  c,  fastened  to  the  under  surface 
of  the  base  serves  to  change  the  direction  of  a  cord  which 
is  tied  to  a  ring  in  the  hard  rubber  button. 

12.  The  belt=spirograph. 

The  apparatus  here  described  was  contrived  to  over- 
come as  far  as  possible  the  objections  which  may  be  raised 


Fig.  59. 
Fig.  59.     The  Belt-spirograph  for  quantitative  determination  of   varia- 
tions in  chest  girth. 

to  the  previously  used  instruments  for  this  purpose.  Note 
in  the  first  place  that  the  wide  elastic  belt  will  follow  faith- 
fully every  movement  of  the  chest  wall,  not  sinking  into 
the  soft  tissues  during  inspirations;  second,  the  almost  in- 
elastic fish  cord  will  transmit  the  movement  of  the  thorax 
much  more  accurately  than  elastic  air  inclosed  within 
elastic  conductors. 

The  59  a,  b  and  c  figures    show   the   construction    ot 
the  belt  spirograph:    (a)   The  2-3   cm.  wide,  elastic    belt 


316 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


showing  location  of  pulleys,  (b)  A  section  of  thorax 
showing  belt  in  position.  The  cord  is  tied  to  an  eye  in 
pulley  No.  1,  passes  around  the  circuit  of  pulleys  to  No.  1 
again,  thence  over  two  or  three  pulleys  which  serve  to 
change  the  direction,  bringing  the  cord  finally  to  a  record- 
ing lever  adjusted  as  described  for  the  thoracometer. 
(c)  Showing  an  enlarged  view  of  a  pulley.  The  brass 
base  of  each  pulley  is  fixed  to  a  piece  of  sole  leather  4  or  5 
cm.  long  by  3  or  4  cm.  wide.  Copper  wire,  riveted  at  the 
points  r  and  r',  clasps  the  elastic  belt  and  holds  the  pulley 

in  position. 

13.    The  stethogoniometer. 

Various  methods  have  been  employed  for  determining 
the  curvature  of  the  chest  wall.     Even  so  simple  a  method 


Fig.  60. 

Fig.    60.      The   Stethogoniometer   used   in   graphically   recording   any 
perimeter  of  the  thorax. 

as  the  taking  of  several  diameters  will  reveal  approx- 
imately the  general  conformation  of  the  chest  wall.  A 
graphic  method  has  this  to  recommend  it  :  that  a  glance  at 
an  outline  of  any  circumference  of  the  thorax  reveals  more 
than  any  amount  of  time  expended  in  the  study  of  numer- 
ical data.  Of  all  the  graphic  methods  used  by  the  writer 
the  one  here  described  seems  most  simple  and  practical. 
The  accompanying  figure  (Fig.  60)  shows  the  instrument, 
which  will   be  recognized  as  similar  to  a  draftsman's  pan- 


APPENDIX  A. 


317 


tograph.  As  used  by  the  draftsman  such  an  apparatus 
enlarges  figures  by  any  multiple  from  1  to  5  in  linear  di- 
mensions, for  that  purpose  the  tracing  stilus  is  placed  at 
a  and  the  recording  pen  or  pencil  at  b,  while  the  point  c  is 
fixed  to  the  table.  As  used  to  trace  the  curvature  of  any 
line  in  the  body,  the  recording  pencil  is  fixed  at  a,  while 
the  point  b  is  made  to  follow  the  curved  surfaces  under 
observation.  In  this  way  records  of  one-fifth  the  linear 
dimensions  of  the  curve  traced  may  be  recorded.  Such  rec- 
ords are  compact  and  readily  filed  for  subsequent  reference. 


Fig    61. 


14.     The    pneo=manometer. 

This  instrument  may  be  easily  con- 
structed in  the  laboratory.  Take  a  piece 
of  heavy  glass  tubing  of  7  to  9  mm.  lumen 
and  at  least  160  centimeters  in  length. 
Bend  it  as  shown  in  Fig.  61.  A  covered 
filter  may  be  attached  as  shown  in  the 
figure  if  there  is  any  tendency  for  the 
mercury  to  be  thrown  out. 

15.     The  chronograph. 

For  many  experiments,  especially  upon 
the  circulation  or  respiration,  it  is  neces- 
sary to  trace  upon  the  rotating  drum,  along 
with  the  record  of  the  circulatory  or  respi- 
ratory movement,  a  record  of  time  in 
seconds  or  known  fractions  thereof.  In- 
struments for  this  purpose  are  to  be  had 
from  the  instrument  houses. 

If  the  student  or  demonstrator  is  in- 
clined to  construct  his  own  chronograph 
the  accompanying  figure   and   description 


The    Fneomano- 

meter.     For  test-   may  be    of   assistance  to  him.      (bee  Jbig 


i  n  g    pressure     in    (J2.) 
forced  respiraiion. 


318 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Materials  and  Construction. —  (1)  A  soft  iron  electro- 
magnet (m)  with  soft  iron  armature  (a),  as  shown  in 
A.  A  machinist  or  electrician  can  construct  these  from 
strictly  pure,  soft  Swedish  iron. 

(2)  No.  24  double  silk  covered  copper  wire,  to  be  wound 
as  indicated  in  A  (x  to  y).  The  wire  should  be  wound 
in  three  layers  and  when  the  winding  is  complete  it 
should  present  the  appearance  shown  in  Fig.  62  B,  m'. 

(3)  From  fiber  board  or  from  wood  one  may  construct 
such  a  lever  and  magnet  support,  as  shown  in  Fig.  60 
B.  The  lever  (1)  is  pivoted  at  f;  the  block  a'  bears 
the  armature;    the  counterpoise  (w)  may  be  adjusted 


Fig.  62. 


Fig.  62. 

The  Chronograph. 


so  as  to  make  the  part  of  the  lever  at  the  right  of  f 
slightly  heavier  than  that  at  the  left,  so  that  when  no 
current  is  flowing  through  the  electro-magnet  the 
armature  is  lifted  from  the  magnet. 

(4)  A  check  (c)  rests  upon  an  adjustable  screw  (s)  and 
limits  the  excursion  of  the  lever. 

(5)  A  straw  may  be  fixed  with  wax  to  the  end  of  the 
lever  and  a  tracing  point  (p)  of  parchment  paper 
slipped  into  the  straw. 

(6)  The  wires  from  the  clock  or  the  chronograph  sys- 
tem are  connected  at  x'  and  y'. 


APPENDIX  A.  31  n 

(7)  The  base  may  be  clamped  to  a  support  and  tie 
tracing  point  adjusted  to  any  height  or  direction. 
This  simple  chronograph  may  be  made  sufficiently  deli- 
cate  to  record  ^-seconds  accurately,  though  seconds  or 
half  seconds  will  usually  answer  the  purposes  of  the  gen- 
eral experiment.  For  very  small  divisions  of  a  second  the 
tuning  fork  should  be  used. 

To  set  up  a  simple  chronograph. — Join  the  chronograph 
and  the  contact  clock  or  a  metronome  in  continuous  circuit 
with  a  common  Daniell  cell.  The  clock  makes  contact 
every  second  or  fraction,  the  armature  is  drawn  down  by 
the  electro-magnet  and  thus  records  the  time  upon  the 
drum  of  a  kymograph. 

16.  The  chronographic  system. 

If  many  students  are  working  at  the  same  time  and  at 
the  same  experiment  in  a  laboratory,  it  is  unnecessarily 
costly  in  both  money  and  space  for  each  student  or  group 
of  students  to  be  supplied  with  separate  chronographic 
clocks  and  batteries.  One  clock  and  a  battery  of  several 
cells  can  be  employed  to  run  ten  or  twelve  chronographs. 
Such  a  chronographic  system  is  too  simple  to  require  ex- 
tended description. 

(1)  Bowditche's  interruption  clock  or  Petzold's  simple 
contact  clock  may  be  hung  in  any  convenient  place  in 
the  laboratory  and  brought  into  circuit  with 

(2)  A  battery,  in  series,  whose  strength  must  depend 
upon  the  amount  of  external  resistance  to  be  overcome, 
i.  e.,  the  number  of  chronographs  in  the  system. 

(3)  The  chronographs  must  be  all  in  one  general  circuit 
rather  than  upon  branches  from  a  primary  circuit. 

(4)  A  loop  of  the  general  circuit  may  pass  to  each 
table  and  the  chronograph  inserted  in  the  loop.  It  is 
hardly  necessary  to  remind   the  demonstrator  that  if, 


320  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

for  any  purpose,  a  chronograph   be  removed   from  a 
table   when   the  system    is   in  operation,  the   general 
circuit  must  be  instantly  completed  by  use  of  a  con- 
■  nector. 

17.  To  prepare  10%,  hydrochloric  acid,  the  acidum  hydro= 
chloricum  dilutum  of  the  U.  S.  P. 

The  concentrated,  c.p.,  hydrochloric  acid  of  a  sp.  gr. 
of  1.16  contains  31.9  per  cent  by  weight  of  HC1  gas.  To 
prepare  10%  HC1,  take  31.4  c.c.  of  the  concentrated  acid 
and  dilute  with  distilled  water  to  100  c.c.  From  this  di- 
lute HC1.  0.2%  HClor0.1%  HC1  or  any  other  desired 
strength  below  10%  may  be  readily  obtained. 


APPENDIX  B. 


APPENDIX  B. 

On  the  general  plan  of  a  course  in  physiology  and  the 
equipment  of  a  laboratory. 

The  following  pages  are  reprinted  from  a  report  of  the 
committee  on  syllabus,  representing  the  Association  of  Ameri- 
can Medical  Colleges.  The  committee  was  in  session  Feb. 
fj~/8,   /8<?6,    Chicago. 

The  course  in  physiology. 

The  course  in  physiology  should  be  continued  through 
two  years  and  should  be,  in  a  general  way,  coordinated 
with  the  course  in  comparative  anatomy  and  general 
biology  and  histology.  By  coordination  in  this  connection 
is  meant  the  arrangement  of  the  courses  in  such  a  way 
that  the  student  shall  learn  first  the  more  fundamental  and 
general  and  then  the  more  special.  To  teach  the  student 
the  physiology  of  the  liver  one  year  and  the  gross  and 
minute  anatomy  of  that  organ  the  next  year  must  be  recog- 
nized by  all  as  an  inversion  of  the  logical  order.  To 
teach  the  anatomy  of  an  organ  one  year  and  its  physiology 
the  next  year  puts  the  teachers  of  both  these  branches 
at  considerable  disadvantage,  and  the  chances  are  great 
that  the  student  will  have  a  less  clear  comprehension  of 
the  subject  presented  in  this  way  than  he  would  if  the 
interval  elapsing  between  the  study  of  the  more  general 
branch   and   the   more  special   branch   be  a   short   one. 

Every  course  in  physiology  should  be  accompanied 
by    laboratory  exercises    in   which   the   student   may   fami- 


334  LABORATORY  GUIDE  IX  PHYSIOLOGY. 

liarize  himself  with  the  technique  of  the  subject  and  may 
demonstrate  for  himself  the  more  fundamental  facts  of  this 
science.  The  laboratory  exercises  should  be  coordinated 
with  the  recitations  and  demonstrations  as  far  as  it  is  pos- 
sible  to  do  so. 

The  first  half  of  the  first  semester  ( eight  weeks")  should 
be  spent  in  a  study  of  the  physiology  of  the  cell  as  il- 
lustrated in  unicellular  plants  and  animals.  While  the 
student  is  studying  the  morphology  of  the  protococcus, 
the  yeast  cell,  the  amoeba  and  the  paramcecium  in  the 
biological  course  he  may  profitably  study  the  physiology  of 
these  organisms  from  such  a  text  as,  "  The  Cell"  (Hett- 
wig),  and  should  repeat  in  the  laboratory  the  experiments 
mentioned  in  Hertwig's  book.  "  AUgemeine  Physi- 
ologic "  (Max  Verworn,  Jena,  1895 )  is  a  valuable  help  to 
the  instructor  who  is  conducting  such  a  course. 

The  second  half  of  the  first  semester  may  be  spent  on 
muscle-nerve  physiology.  Having  already  studied  the 
reaction  of  amoeba  and  paramcecium  to  electricity,  and  hav- 
ing studied,  in  general  histology,  the  structure  of  muscle 
fibers  and  cells,  and  nerve  fibers  and  cells;  further  having 
made  careful  dissections  of  frogs  and  other  vertebrate  ani- 
mals the  student  is  in  a  position  to  comprehend  and  appre- 
ciate the  reaction  of  muscle  tissue  in  response  lo  various 
direct  stimuli  and  to  indirect  stimuli  applied  to  the  nerve. 
The  frog-heart  and  the  "muscle-nerve  preparation"  are 
most  used  for  such  experiments. 

Beginning  with  the  second  semester  or  second  half  of 
the  first  year  the  general  subject  of  nutrition  should  be  be- 
gun. Whether  one  introduces  this  field  of  physiology 
with  the  study  of  the  circulatory  system  or  of  the  digestive 
system  is  a  matter  of  little  consequence.  The  problems 
of  the  circulation  being,  for  the  most  part,  physical  prob- 
lems, would  seem    to  justify  the  consideration  of  that  sub- 


APPENDIX  B.  325 

ject  first,  followed  by  the  respiratory  system,  which  pre- 
sents simple  problems  in  mechanics,  physics  and  chem- 
istry. The  student,  having  in  the  meantime  made  some 
progress  in  physiological  chemistry,  is  able  to  comprehend 
the  general  features  of  the  chemical  problems  involved  in 
digestion,  and  should  now  enter  upon  a  systematic  consid- 
eration of  nutrition  :  1,  food  and  foodstuffs;  2,  prepara- 
tion of  foods;  3,  mastication;  4,  deglutition;  5,  salivary  di- 
gestion; 6,  gastric  digestion;  1,  intestinal  digestion;  8,  ab- 
sorption; 9,  distribution;  10,  assimilation  or  anabolism ;  11, 
katabolism  and  animal  heat,  and  12,  excretion.  This  course 
will  probably  consume  the  second  semester  of  the  first  year 
and  apart  or  all  of  the  first  semester  of  the  second  near. 
The  remaining  time  allotted  to  physiology  should  be  de- 
voted to  the  physiology  of  the  nervous  system,  the  phys- 
iology of  the  special  senses,  and  the  physiology  of  repro- 
duction. All  of  these  courses  should  be  accompanied  by 
laboratory  work. 

After  the  student  has  completed  the  above  required 
courses  he  should  be  given  an  opportunity  to  elect  special 
courses  in  physiology  during  the  second  semester  of  the 
second  year  and  during  the  third  year.  Profitable  elective 
courses  would  be,  for  example:  1.  Physiology  of  intra- 
uterine life,  following  Preyer's  "  Physiologie  des  Embryos;" 
2.  Special  problems  in  the  physiology  of  digestion,  follow- 
ing Brunton  in  "Handbook  for  the  Physiological  Labora- 
tory; "  3.  Physical  examinations  of  the  blood,  using  hema- 
tokrit,  hemometer,  corpuscle  counter,  micrometer  and 
staining  methods;  4.  Experimental  physiology  of  the  cen- 
tral nervous  system,  following  Cyon;  5.  Physiological 
psychology,  following  Wundt  or  Ladd.  The  instructor 
may  get  much  help  from  such  works  as  Cyon's  "  Methodik 
der  Physiol.  Experimente;  "  Gscheidlen's  "  Physiologische 
Methodik;"     Foster    and    Langley's    "Practical    Physiol- 


32G  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

ogy;  "  Schenck's  "  Physiologisches  Practicum;  "  Brunton 
and  Burdon-Sanderson's  "Handbook  of  the  Physiolog- 
ical Laboratory;"  McGregor-Robertson's  "Physiological 
Physics;"  Langendorf's  "  Physiologische  Graphik,"  and 
Stirling's  "Practical  Physiology." 

The  organization  and   equipment  of    the  department  of 
physiology. 

Inasmuch  as  many  of  the  colleges  of  the  Association 
have  not  yet  established  physiological  laboratories,  it  is 
thought  well  to  give  a  few  general  hints  on  the  subject. 
The  imposing  equipments  which  one  sees  in  the  physiolog- 
ical institutes  of  Europe,  equipments  which,  in  the 
aggregate,  have  cost  many  thousands  of  dollars,  over- 
awe one  and  make  one  hesitate  to  advise  the  undertaking 
of  so  great  a  task,  so  we  are  letting  the  years  slip  by  with- 
out establishing  physiological  laboratories.  We  must  not 
forget  that  the  equipment  of  European  laboratories  is  a 
growth  which  has  covered  many  decades;  and  further, 
that  it  is  really  advisable  to  allow  a  department  to  grow, 
collecting,  in  the  course  of  a  few  years,  an  equipment 
which  is  perfectly  adapted  to  the  wants  of  the  institution 
and  to  the  special  methods  of  the  head  of  the  department. 
The  committee  strongly  advises  the  early  establishment 
of  physiological  laboratories,  even  if  an  institution  cannot 
appropriate  for  the  purpose  more  than  $1,000  to  start 
with.  If  an  institution  can  devote  to  this  department  a 
well-lighted  general  laboratory  room  36  ft.  to  40  ft.  square, 
with  two  or  three  small  rooms  for  instrument  room,  work- 
shop and  library,  and  can  appropriate  $1,000  to  $l,f>00  for 
the  first  equipment,  then  a  laboratory  fee  of  $5  annually 
from  each  student  who  works  in  the  department  will,  in 
the  course  of  a.  decade,  produce  a  sufficiently  full  equip- 
ment for  all  practical  purposes. 


APPEXDIX  P.  327 

At  this  point  it  may  be  well  to  give  a  hint  as  to  the 
organization  of  the  department,  as  this  determines  largely 
the  character  of  the  equipment  and  the  number  of  dupli- 
cations of  each  instrument. 

The  amount  of  personal  supervision  required  by  the 
student  in  practical  physiology  is  so  great  that  it  is  in- 
expedient to  attempt  to  conduct  large  classes.  A  demon- 
strator and  one  assistant  demonstrator  cannot  properly 
supervise  the  work  of  more  than  thirty  students  at  one 
time,  even  though  each  student  be  provided  with  a  labora- 
tory manual.  In  the  organization  and  equipment  here 
planned  let  it  be  understood  that  the  laboratory  class  work 
in  sections  of  thirty  students  each,  and  that  each  section  be 
subdivibed  into  ten  divisions  of  three  students  each.  Now, 
experience  in  many  laboratories  has  shown  that  a  student 
will  accomplish  practically  as  much  in  one  laboratory 
period  of  three  hours  as  in  two  laboratory  periods  of  two 
hours  each.  The  three-hour  laboratory  period  promotes 
economy  both  for  the  student  and  for  the  department. 
Following  this  arrangement,  two  instructors  would  be  able 
to  supervise  the  work  of  180  students,  meeting  one  sec- 
tion of  thirty  students  each  day.  With  this  allotment  of 
time  each  student  would  have  three  hours  of  laboratory 
work  each  week  during  the  year,  which  would  enable  him 
to  demonstrate  for  himself  all  of  the  fundamental  princi- 
ples of  physiology.  In  the  question  of  the  choice  between 
(1)  the  condensation  of  180  hours  of  laboratory  work  in 
physiology  into  a  period  of  sixty  days  with  three  hours  per 
day,  and  (2)  the  distribution  of  the  same  number  of  hours 
over  sixty  weeks  (two  years)  with  three  hours  per  week, 
and  its  coordination  with  theoretical  work  in  physiology 
and  with  the  courses  in  gross  anatomy  and  histology,  we 
would,  without  a  moment's  hesitation,  decide  in  favor  of 
the  latter  plan. 


328  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

If  this  general  plan  of  organization  be  adopted,  and  if 
the  department  wishes  to  provide  for  sections  of  thirty 
students,  working  in  ten  divisions  of  three  students  each, 
then  the  apparatus  should  be  duplicated  in  tens.  The  fol- 
lowing list  of  apparatus  is  suggested  as  a  practical  one 
with  which  to  make  a  beginning  :  * 

EQUIPMENT    FOR    GENERAL     LABORATORY   WORK. 

10  strong  tables,  6  feet  by  3  feet,  $5  CO $  50.00 

1 0  kymographs,  $35 35000 

20  Daniell's  cells,  quart  size,  $1.75 37.50 

4  pounds  of  copper  wire,  No.  IS  double  cotton  cover,  50c. .  . .  2.00 

y2  pound  copper  wire,  No.  24  double  silk  cover,  $2  00 1.00 

10  simple  compasses  (for  detectors),  30c 3.00 

10  contact  keys,   $1.25 12.50 

10  Du  Bois  keys,  $3.25 32.50 

10  simple  rheocords,  $2.50 25.00 

10  Du  Bois  Reymond  induction  machines,  $17. 5u 175.00 

10  Pohl's  commutators,  with  crossbars,  $4.50 45.00 

10  pairs  of  tambour  pans,  $2.00 20  00 

20  heavy-base  stands,   $1.00 20.00 

Fixtures  for  same — 

2  right  angle  clamp-holders,  extra  heavy $0.50 

1  universal  clamp-holder 0.75 

1  extension  ring  (4  inches) 0.25 

1  Muscle  forceps,  cork  insulation 1.00 

1  simple  myograph 2.50 

10  of  each $5.00  50.00 

10  Bunsen  burners,  35c   3.50 

10  bell  jars,  80c   8.00 

10  double  valve  rubber  bulbs,  large  size,  50c 5.00 

5  haemometers  (Fleischl's),  $12.50 62.50 

5  sphygmographs.  $20.00 100.00 

5  blood  corpuscle  counters  (Zeiss),  $17.50   87.50 

*In  reprinting  the  following  list  the  auihor  has  taken  the  liberty  to 
revise  his  earlier  list  as  published  in  the  report  of  the  committee.  As 
revised  it  provides  for  a  higher  class  of  apparatus  at  a  proportionately 
higher  price,  but  brings  the  aggregate  down  to  the  former  estimate  by 
reducing  the  number  of  incidentals. 


APPENDIX  B.  329 

General  surgical  appliances,  forceps,  shears,  etc 25.00 

10  pounds  assorted  sizes  of  glass  tubing,  35c 3.50 

Assorted  sizes  of  soft  rubber  tubing 3.00 

Rubber  stoppers,  assorted  sizes,  perforated 2.00 

Corks  and  sheet  cork 2  <  10 

Cork  borers,  Files,  for  cutting  glass  tubing . .  2.50 

2  gas  generators,  Kipp's,   $3.50 ;  00 

Graduated  cylinders,  pipettes,  flasks,  bottles,  beakers,  etc 25.00 


$1,160  00 


INSTRUMENTS    FOR    SPECIAL    USE    AND    FOR    DEMONSTRATIONS. 

Detector $     2.50 

Galvanometer 50.00 

Rheostat  or  plug  resistance  box  of   12  coils 10.00 

Metronome,  mounted  to  make  and  break  circuit 12.00 

Contact  clock 25.00 

Tuning  fork,  electrically  maintained,  mounted  for  tracing 25.00 

Chronograph 10.00 

Hsematokrit 25  00 

Plethysmograph 6.50 

Quantitative  balances 30  00 

1  pair  dog  scales   15.00 

Laboratory  balances 10.00 

Mercurial  manometer  for  blood  pressure 10.00 

Ludwig  rheometers 1 5. (10 

Moist  chamber 20.00 

Muscle  forceps 3. 50 

Capillary  electromometer  (Kiihne's) 5.00 

Du  Bois-Reymond  rheocord 25.00 

Hot  air  motor 40. 00 

Still  for  making  distilled  water 15.00 

Drying  oven,  10x12,  double  wall 13.00 

Apparatus  for  determining  focal  distances 2  50 

Steel-calipers 5  00 

Spirometer 10  00 

Stethogoniometer,  belt  spirograph  and  pneomanometer 15.00 

$400  00 
This  list  might  easily  be  extended  to  amount  to  several 

thousand  dollars,  but  it  is  intended  here  to  include  only 
those  instruments  which  seem  necessary  to  start    with. 


330  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

THE    WORK    SHOP. 

Demonstrators  and  students  can  easily  construct  in  a 
shop,  many  pieces  of  simple  apparatus,  which  if  pur- 
chased of  some  instrument  house,  would  amount  to  many 
times  the  cost  of  the  material  and  would  deprive  students 
of  some  very  valuable  experience.  Frog,  rat,  rabbit  and 
dog  holders  may  be  made,  the  tambour  frames  may  be 
furnished  with  membranes  and  mounted  as  receiving  or 
recording  tambours,  cardiographs,  or  stethographs.  All 
writing  levers,  electrodes,  etc.,  should  be  made  by  the 
students.  A  room  with  bench  and  vice  and  $25  for  car- 
penter's and  machinsts'  tools  would  be  an  ample  start. 

A    FEW  NECESSARY  CHEMICALS. 

20  pounds  CuS04 $  1  40 

10  pounds  H2S04 75 

5  pounds  mercury 3.30 

2  pounds  kaolin  (for  electrodes,  etc.) 10 

1  dram  of  curare 1. 25 

5  pounds  gum  da  mar 125 

20  pounds  benzol 4.00 

10  pounds  chloroform  (imported  duty  free) 5  00 

10  pounds  sulphuric  ether  (imported  duty  free) 3  00 

5  pounds  unmedicated  surgical  cotton  at  25  cts 1.25 

2  pounds  sealing  wax  in  sticks '. 1 .00 

5  pounds  plaster  of  Paris 50 

5  gallons  alcohol  (96$)   

1  gallon  abs.   alcohol 

2  pounds  sodium  hydrate 

2  pounds  magnesium  sulphate 

2  pounds  sodium  chlorid  (pure) 

2  pounds  glycerin 

1  pound  hydrochloric  acid , 

1  pound  nitric  acid 

1  pound  ammonium  hydrate 

Drugs  as  listed  under  Pharmacology 


About  $35.00 


APPENDIX  B.  331 

A  WORKING   LIBRARY  OF  PHYSIOLOGY. 

Beside  the  laboratory  manuals  enumerated  under  the 
"Course  in  Physiology,"  we  mention  a  few  journals  and 
general  works  that  should  be  in  every  laboratory  of  physi- 
ology :  Hermann's  "  Handbuch  der  Physiologie";  Journal 
of  Physiology,  ed.,  Michael  Foster,  Cambridge,  England; 
Pfliiger's,  Archive  f.  d.  gesammte  Physiologie,  Bonn,  Ger- 
many; Archiv  fur  Anatomie  and  Physiologie,  [phvsiol.  part] 
ed.,  Du  Bois-Reymond,  Berlin,  pub.,  Yeit  &  Co.,  Leipsig  ; 
Centralblatt  fur  Physiologie,  pub.,  France  D^uticke,  Leipsic; 
Journal  of  Experimental  Medicine  [physiological  part  edited 
by  Bowditch,  Chittenden  and  Howell],  D.  Appleton  & 
Co.;  "Animal  Physiology,"  Mills,  D.  Appleton  cSc  Co., 
1889;  "Text-book  of  Physiology,"  Michael  Foster,  Mac- 
millan,  1888  93;"  "Human  Physiology,"  Landois  and 
Stirling,  Blackiston,  Philadelphia,  last  edition;  "  Refrac- 
tion and  Accommodation  of  the  Eye,"  Landolt,  Lippin- 
cott,  Philadelphia,  1886;  "The  Frog,"  Marshall,  London, 
1894;  "Anatomy  of  the  Frog,"  Ecker,  Oxford,  1889  : 
"The  Cat,"  Mivart,  Scribner,  1881;  "Dissection  of  the 
Dog,"  Howell,  Holt  &Co.,  1888;  "Anatomie  des  Hundes," 
Ellenberger  &  Baum,  Berlin,  1891  ;  "  Dictionary  of  Medi- 
cine," (4tO),  Gould,    Blackiston,    Philadelphia,  1895. 

Beside  these  there  should  be  recent  representative 
manuals  of  histology,  general  biology,  embryology,  chem- 
istry and  physics. 

PHYSIOLOGICAL    CHEMISTRY. 

It  has  been  taken  for  granted  that  the  chemical  prob- 
lems of  physiology  will  be  assigned  to  the  department  of 
chemistry.  The  equipment  of  that  department  makes  such 
a  division  of  the  subject  highly  advantageous.  For  years 
urine  analysis  has  been  taught,  usually  in  the  second  year 
of  the  course  in  the  department  of   chemistry.      Many  of 


332  LABORATORY  GUIDE  IN  PHYSIOLOGY. 

the  stronger  institutions  have  long  since  expanded  the  sec- 
ond year  course  in  chemistry  into  a  very  creditable  course 
of  physiological  chemistry,  beginning  with  an  investiga- 
tion of  foodstuffs,  following  this  with  qualitative  and 
quantitative  work  on  the  chemistry  of  digestion,  and  de- 
voting the  last  semester  of  the  second  year  to  the  analysis 
of  urine.  The  best  laboratory  manuals  on  the  subject  are  : 
Long's  "Laboratory  Manual  of  Chemical  Physiology," 
Colegrove&  Co.,  Chicago,  1395;  Stirling's  "Practical  Phys- 
iology" (first  part);  Halliburton's  "Essentials  of  Chemical 
Physiology'"  Longmanns,  Green  &  Co.,  1893.  The  phy- 
siological library  should  contain  also:  "Text-book  of 
Chemical  Physiology  and  Pathology,"  Halliburton,  Long- 
manns, Green  &  Co.,  1891  ;  "  Physiologische  Chemie," 
Bunge,  Vogel,  Leipzig,  1894  ;  "  Lehrbuch  d,  physiologisch, 
Chemie,"  Neumeister,  Gustav  Fischer,  Jena,  1893;  "Phy- 
siological Chemistry,"  Hammarsten,  Wiley  &  Sons,  New 
York,  1893  ;  "  Physiological  Chemistry  of  the  Animal 
Body,  "Gamger,  Macmillan,  1893;  "Chemical  Physiology 
and  Pathology,"  Hoppe-Seyler. 


APPENDIX  C. 


APPENDIX    C. 


It  is  proposed  at  this  point  to  devote  a  few  pages  to  the 
illustration  and  brief  description  of  the  more  important 
instruments  and  glassware  which  go  to  make  up  a  prac- 
tical equipment  for  a  physiological  laboratory. 

i.     Physical  Apparatus.* 

1.  The  Kymograph. — The  basis  of  the  instrumentarium  of  the 
physiological     laboratory   is    the     kymograph.     It    is    in    almost     con- 


Fig    1.      Kymograph. 


*For    the  plates  in  this  section  I  am  indebted  to  the  Chicago  Lab- 
oratory Supply  and  Scale  Co.,  29  West  Randolph  St.,  Chicago. 

335 


336 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


stant  use  in  muscle-nerve  physiology,  in  circulation,  in  respiration, 
and  in  pharmacology.  It  must  be  portable,  durable,  accurate,  read- 
ily adjustable  as  to  speed  and  height  of  drum.  All  of  these  quali- 
ties, together  with  reasonable  cheapness,  are  possessed  by  the  kym- 
ograph illustrated  in  the  accompanying  figure.  This  instrument 
was  designed  by  Mr.  C.  H.  Stoelting,  of  Chicago,  for  use  in  the 
physiological  laboratory  of  the  University  of  Chicago.  It  is  now 
used  in  the  University  of  Michigan,  Northwestern  University,  Mas- 
sachusetts Institute  of  Technology  and  the  State  Universities  of 
Illinois,  Texas  and  Colorado,  in  Rush  Medical  College,  and  the 
Detroit  Medical  College. 

The  height  of  the  instrument  is  55  cm.;  weight  15  ko.  The 
drum  is  propelled  by  a  clockwork,  which  is  under  perfect  control 
of  the  operator. 


Fig.  la. 
Fig.  a.     Drum  supporter  with  drum  and  burners. 


2.  The  Myograph,  a.  The  spring  myograph,  modified  from  Du 
Bois  Reymond's.  b.  Simple  myograph  as  used  in  the  physiological 
laboratory  of  the  Northwestern  University,  and  shown  in  Fig.  2. 
c.   The  crank  myograph. 


.U  TEND IX  C. 


337 


Fig.  2. 

3.  The  Chronograph  time-marker.     Figure  4  shows  Dr.  Lingle's 
modification  of  Pfief's  single  chronograph. 


Fig.  3. 


338 


LABORATORY  GUIDE  IN  PHYSIOLOGY 


4.  The  Marey  Tambour.     See  Fig.  4. 


Fig.  4. 
5.   The  Pohl  Commutator.     See  Fig.  5. 


Fig. 


6.  The  Introduction  Coil  or  Inductorium.  Figure  6  shows 
DuBois-Reymond's  instrumen).  Ludwig's  instrument  consisted  in 
changing  the  axia  of  the  coils  to  the  vertical  position  and  counterpoising 
the  secondary  coil.  The  DuB-R.  instrument,  or  some  modification  of  it, 
is  in  more  general  use,  and  is  satisfactory. 


APPENDIX  C. 


339 


Fig.  6. 


Fig. 


Fig.  8. 


7.  The  Muscle  Forcips.  a.  Figure  8  snows  a  fine  brass  instru- 
ment with  insulated  jaws  and  a  binding  post,  b.  A  simpler  and  cheaper 
form,  with  cork  insulation,  and  without  the  binding  post,  answers  all 
ordinary  purposes. 

8.  The  Detector,  or  low  resistance  galvanometer,  is  shown  in 
Figure  8. 

8a.  The  Galvanometer,  <i,  Eblemann's  universal;  />.  Rosenthal's 
physiological. 


340  LAB  OK  A  TOR  ) "  G  VIDE  IN  PHYSIOL  OGY. 

A  i|»  ...|   Soon 


Fig.  10. 
10.     The  Compensator.    Ludwig's  instrument  is  shown  in  figure  10. 


Fig.  11.  Fig.  11a. 

11.     Batteries,     a.   The  Daniell  cell,  or  element,  is  shown  in  fig- 
re  11.    b.   The  Bichromate  cell — see  figure  11a. 


APPEXPIX  C. 


341 


Fig.  12. 

12.     The    Rheocord.     //.    Dubois-Raymond's    Rheocord.     b.   The 
simple  rheocord  as  shown  in  figure  12.     c.   The  Oxford  rhecord. 


Fig.  13. 

18.  Electrodes.  Figure  13  shows:  a.  Hand-electrodes  of  insu- 
lated copper  or  platium  wires  for  use  with  induced  currents.  /'.  Xon- 
polarizable  electrodes,  variously  constructed.     For  description  see  text. 


342 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Fig.  14. 


Fig.  14a. 


Fig.  14b. 


Fig.  14c. 


14.  Binding  Posts.     Various  forms  are  shown  above. 

15.  Binding  Connectors.    Constructed    of    brass   and    in    varying 
forms. 


Fig.  16. 


Fig.  16a. 


16.  Keys.  a.  DuBois-Reymonds  key  with  knife-edge  contact. 
b.  The  mercury  key,  as  shown  in  figure  16a.  c.  The  spring  contact  key 
(Fig.  12K).     d.   The  Morse  key. 


APPENDIX  C. 


343 


Fig.  17. 


u 


Fig.  17a.  Fig.  17b. 

17.  Anthropometric  Instruments.  These  are  various  and  consist 
of  scales,  meter  tape,  calipers,  dynamometers,  spirometer,  etc.,  etc. 
Fig.  17  shows  the  belt-spirograph  used  to  make  a  quantitative  deter- 
mination of  variations  of  chest  girth.  Fig.  17a  shows  the  pneo-manom- 
eter  for  testing  forced  respiratory  pressure.  Fig.  17b  shows  the 
stethogoniometer,  for  making  a  graphic  record  of  the  chest  perimeter. 


344 


LABORATORY  GUIDE  IN  PHYSIOLOGY 


Fig.  19. 

18.  Still.   For  making  distilled  water. 

19.  Support.     Special   pattern    for    physiology,    with    extra    heavy 
base   length  50-75  cm.,  weight  2%  Ko.-4>£  Ko. 


Fig.  20. 

20.   Drying  Oven,  with  double  wall  10  in.  by  12  in.     May  be  used 
for  incubator  in  experiments  in  digestion. 


APPEXDIX  C. 
II.     Chemical  Apparatus. 


345 


Fig.  28. 

2?.   Analytical  Balance,  Becker's  short   beam,  for  a  charge   up   to 
100  g.  in  each  pan.     Sensitive  to  ^  rag.  with  rider  apparatus. 
28.   Analytical  weight,  Becker's,  100  g.  down. 


*Forthe  plates  In  this  section  I  am  Indebted  to  Richard  &  Co.,  108  Lake  St. 
Chicago. 


346 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Fig    29a. 


Fig.  2!Jb. 


29a.   Balance  for  laboratory  work.     Capacity,  2  pounds.     Sensitive 
to  1-20  grain. 

29b.  Weights  500  g.  down,  in  polished  block. 


APPEXDIX  C. 


347 


Fig.  30.     Fig.  31.       Fig.  32. 


Fig.  33. 


Fig.  34.         Fig.  35. 


30.   Gay  Lussac's  burette,  on  wooden  base,  25  c.  c.  in  1-10. 
31a.   Mohr's  burette,  w.  pinchcock,  50  c.  c.  in  1-5. 
31b.   Mohr's  burette,  w.  pinchcock,  100  c.  c.  in  1-5. 

32.  Graduated    cylinders   with  lip,  double  graduation,  10  c.  c  ,   50 
c,  100  c.  c,  250  c.  c  ,  500  c.  c,  1,000  c.  c.  and  2,000  c.  c. 

33.  Graduated   cylinders,   stoppered,  100  c.  c,  500  c.  c.  and   1.C00 


34.  Volumetric  flask,  1,000  c.  c. 

35.  Bottle  for  mixing,  glass  stoppered,  250  c.  c,  500  c.  c,  1,000c.  c. 


348 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Fig.  36. 


Fig 


Fig.  38. 


36.  Evaporating  dishes  in  nests  of  9,  from  2  oz,  to  20  oz. 

37.  Evaporating   dishes,   best  German  porcelain,   heavy  rim,  nests 
of  five,  from  %  to  1  gal. 

38.  Flasks,  vial  mouth. 


Fig.  39. 

39.  Beakers,  plain' 3  oz. -50  oz. 

40.  Beakers.  Griffin,  lipped,  5  oz.-64  oz. 


Fig.  40. 


APPENDIX  C. 


:;}'.i 


Fig.  41. 


Fig.  42. 


Fig.  43. 


41.  Glass  funnels,  best  German,  2  in.  to  8  in. 

42.  Glass  funnels,  ribbed,  3)4  in.  to  8  in. 

43.  Liter  Erlenmeyer  flasks,  Jena  glass. 


Fig.  44. 


Fig.  45. 


Fig.  46. 


44.  Calcium  chloride  tubes,  Schwarz,4-4. 

45.  Potash  bulbs,  Geissler's,  with  drying  tube. 

46.  Woulf-bottles,  1  pint  size  and  1  qt.  size. 


350 


LABORATORY  GUIDE  IN  PHYSIOLOGY. 


Fig.  47. 


Fig.  48. 


47.  Bell  glasses,  low  form,  with  knob,  6  in.  diam. 

48.  Bell  glasses,  tall  form,  with  knob,  7>z  in-  diam. 

49.  Bell  glasses,  open  top,  6  in.  diam. 


Fig.  49. 


Fig.  50. 


Fig.  51. 


Fig.  52. 


50.  Bell  glass,  open  top,  with  tubulure  at  side,  yz  gal. 

51.  Bottles,  extra  wide  mouih,  4  oz.  to  16  oz. 

52a.   Bottles,    mushroom,    glass   stopper,    narrow   mouth,    4  oz.  to 
16  oz. 

52b.  Bottles,  mushroom,  giass  stopper,  narrow  mouth,  16  oz. 


APPEFDIX  C. 


351 


8 


Fig   53. 


/] 


Fig   54. 


£  w 


Fig.  53. 


53.  T-tubes. 

54.  Y-tubes. 

55.  Kipp's  gas  generator,  1  qt. 

56.  Thermometers,  150  degrees  C. 


I 


Fig.  56. 


INDEX. 


PAGE 

Abreast,  arrangement  of  cells.  .     35 

Absorption 189 

Accommodation ,.   216 

range  of 238 

Acetic  acid  in  gastric  digestion.    173 

Aconite 303 

Acuteness  of  vision 232 

Adaptation  of  eye  for  direction.   210 

for  distance 216 

Adipose  tissue,  action  of  gastric 

juice  on 172 

Age,  effect  on  range  of  accom- 
modation    211 

Albumin,    preparation    of    acid 

albumin 162 

preparation  of  egg  alb.    ...    161 
Alcohol,  effect  on  ciliary  motion     22 

Amalgamation  of  zinc 27 

Amperes,  unit  of  current 31 

Amplitude  of  convergence 241 

Amylolytic  ferment 187 

Anaesthesia Ill 

Anelectrotonus 76 

Anode 2S 

Anode  Pole,  influence  of 51 

Anthropometric  data 127 

Appendix  A 307 

Apex  beat 91 

Apparatus  for  determining  focal 

distances 202 

Arterial  pressure 104 

Astigmatism 237 


PAGE 

Atropin 290 

Average  vs.  median  value 128 

Batteries 308 

grouping 34 

Belt  spirograph 315 

spirograph 118  121 

Bile  pigments,  Gmelins  test  for.  186 
Bile,    preliminary    experiments 

on 185 

Biuret  test 104 

Binocular  fixation 220,  242 

Blind  spot 223 

calculate  size  of   223 

map  out 223 

Blood    pressure,   influenced    by 

digitalis 301 

laws  of 102 

Blood,  examination  of  fresh...  259 

Blood  corpuscle  counter 261 

Bone  marrow,-  study  of 281 

Break  induction  shock 71 

Bread,  action  of  saliva  upon.  .  .  158 

Brush  electrodes 52 

Calipers 124 

Capacity  of  Lungs 124 

Carbon-dioxide   gas,    effect    on 

ciliary  motion 21 

determination  of 1-40 

Carbohydrates 153  156 

Cardiogram 92 

Cardio-pneumatogram 139 

Cardiograph 91 

353 


354 


INDEX. 


PAGE 

Cardiograph 311 

Cardinal    points    of    simple   di- 
optric system 207 

Cells,  galvanic 308 

Cell,  work  done  by 29 

Chemical  stimulation 60 

Chloroform,    effect     on     ciliary 

motion 21 

Chronograph 317 

system 319 

Ciliary  motion 16 

Circulation,   capillary 85 

Circulatory  system,  artificial. . .   102 

Circuit,  short  and  long 40 

primary  and  secondary.  ...      70 
Citric  acid  in  gastric  digestion  .   173 

Conjugate  focal  distances 203 

Color   sense 238 

perimeter .   230 

Commutator,  Pohl's  (Fig.  5).  .  .  28 
Compensator,  Ludwig  (Fig.  8)  .  46 
Constant    current,     stimulation 

with 68 

Convergence 216,   221 

amplitude  of 241 

to  measure 241 

negative 245 

Counting  white  corpuscles 265 

red  corpuscles 262 

red  and  white  corpuscles. .   268 

Curare 287 

Curarize  a  frog 309 

Current,  polarizing 76 

how  measured 31 

change  of  course 29 

change  of  direction 28 

Curvature,   radius  of 201 

Daniell  cell 27 

Data,  anthropometric 127 

evaluation  of 127 


PAGE 

Data,  grouping  of 127 

preservation  of 125 

Descending  current 68 

Detector  (Fig.  6) 35 

Dextrin,  properties  of 154  155 

Diameters  of  chest 124 

Diaphragm,  action  of 132 

tactile  observation  of 133 

Diffusibility  of  fat-derivatives. .  184 

of  proteids 166 

Digestion  and  absorption,  intro- 
duction    150 

salivary 157 

gastric 171 

Digitalis 300 

influence  on  blood  prts.  .. .  301 

Dilute  hydrochloric  acid 320 

Dioptric  system  (Fig   29,  A)...  207 

Direct  vs.  indirect  stimulation . .  26 
Discharge   of    liquids    through 

tubes 95 

relation  of  to  resistance.  . .  95 

Dissection  of  eye 192 

Distance,   pupillary 244 

Dyne 24 

Elastic  tubes,  flow  of  water  in.  98 

Elasticity  of  rabbit's  lurg 138 

Electrical  units 31 

Electricity  as  a  stimulus 65 

Electrodes  (Fig.  9) 52 

Electrolysis,   a   measure   of    E. 

M.    F 30 

Electromotive  force,  how  meas- 
ured    31 

Electrodes,   positive    and   nega- 
tive   28 

Electrotonus 75 

laws  of 79 

Emmetropia 237 

Emulsion 183 


INDEX. 


355 


PAGE 

Endosmotic  equivalent 191 

Endosmotic  pressure 190 

Energy,    electrical 30 

Erg 24 

Ergs  of  muscle  work 74 

Ether,  effect  on  ciliary  motion.     22 

Evaluation  of   data 127 

Eye,  adaptation  of  for  distance.   216 
adaptation  of  for  direction.   219 
application    of   laws  of  re- 
fraction to 210 

dissection  of 192 

the  reduced 211-212 

to  locate  cardinal  points  in.   212 

skiascopic 247 

Extra  polar  region 76 

Extract  of  pancreatic  ferments.   185 

Far  point 218 

Falling  bodies,  law  of 94 

Fats,  emulsification  of 183 

Fats,  saponification  of 182 

Fat-splitting  ferment 187 

Fehling's  solution 153 

Ferment 186 

amylolytic 187 

fat-splitting 187 

milk-curdling 187 

proteolytic ; . . . .  187 

Fixation  binocular 220-242 

monocular 219 

Fixing  fluid  for  tracings 311 

Fixing  the  spread,  haematology .   278 
Flow  of  liquids  through  tubes. 93,  98 

Focal  distances,  conjugate 203 

apparatus  for  determining.   201 

Focal  distance  of  lenses 201 

Form  sense,  to  test 234 

Fovea  centralis,  shadows  of...   225 
Frog-boards 307 


PAGE 

Frog's   heart-beat,  graphic  rec- 
ord of 89 

Frog's  heart,  the  action  of.  .  .  .87-89 

Frog's  thigh,  anatomy  of 57 

Galvanic  cells 308 

Galvanismus 75 

Gastric  digestion,    influence  of 

NaCl  on 177 

influence  of  mechanical  di- 
vision on 1 78 

influence  of  temperature  on  179 

steps  of ISO 

active  factors  of 172 

acid  factor  of 173 

Gastric  juice,  preparation  of   .    171 

Standard 175 

Gastrocnemius  preparation.  ...     57 

Girth  of  chest 124 

Glass,  to  measure  index  cf  re- 
fraction    200 

Gmelin's  test  for  bile  pigments.    186 

Hand  electrodes 52 

Haematology,  microscopic  tech- 
nique     276 

Hasmatocrit 271 

Haematology 257 

Hasmogloblin,  estimation  of  .  .  .    273 

Haemometer,  Fleiscbl's 213 

Heart-sounds 91 

Height 125 

Holder,  for  rabbit  (Fig.  19) 110 

Hydrochloric  acid  in  gastric  di- 
gestion  173-174 

influence  of  on  putrefaction   177 
Hydrochloric  acid  dil  ,  to  pre- 
pare     320 

Hydrogen,  respiration  in 145 

Hyperopia .    237 

Illuminating  gas,  respiration  in,   148 


356 


INDEX. 


PAGE 

Images,  Purkinje-Sansom's.  .. .  223 

Impulse  wave 99 

Inelastic  tubes,  flow  of  water  in,  98 

Index  of  refraction  of  water.  . .  199 

of  glass 200 

instrument  for  determ....  199 

Induction  shock,  make 70 

break 70 

Intermittent  pressure,  influence 

of    98 

Intestinal  digestion 185 

Intra-abdominal  pressure 114 

Intra-polar  region 16 

Intra-thoracic  pressure 114 

to  measure 1 16 

Kaolin  for  electrodes 51 

Katelectrotonus 76 

Kathode 28 

Kathode  pole,  influence  of. ...  51 

Key,   Du  Bois-Reymond  (Fig. 4)  29 

simple  contact,  (Fig.-7-K  ).  43 

the  mercury,  (Fig.  3. ) 29 

Kymograph 62 

to  smoke  Drum 310 

Lactic  acid  in  gastric  digestion.  173 

Lactose,  properties  of 155,  156 

Law  of  contraction,  Pfltiger's.  .  80 

of  electrotonus 79 

of  falling  bodies 94 

of  kathodic  and  anodic  in- 
fluence    55 

ofTorricelli 94 

Lenses,  focal  distance  of 201 

Leucocytes,  varieties  of 280 

Lever,  for  transmitting  dia- 
phragm movements 133 

Lenses,  numeration  of 232 

Light,  perimeter 229 

Light,  sense 237 


PAGE 

Liquids,  flow  of  through  tubes 

93-98 

Lung  capacity 124 

Macula  lutea 225 

Maltose,  properties  of 155,-156 

Make  induction  shock 70 

Manometer,  mercurial 103 

Marriotte's  experiment 223 

Maxwell's  experiment 225 

Mechanical    stimulation 59 

Median    value 128  -129 

Mercurial  manometer 103 

Meter-angle  of  convergence.  .  .  244 
Millon's  reagent,  preparation  of  162 
Milk,  chemistry  of 167-170 

gastric  digestion  of 180 

Milk-curdling   ferment 187 

Monocular  fixation 219 

Movements,  respiratory 113 

Multiple-arc,     arrangement     of 

cells 35 

Muscle-nerve   preparation 56 

Muscle-telegraph,  Du  Bois-Rey- 
mond      48 

Myograph,  double  (Fig.  10) 53 

simple  (Fig.    13) 59 

Myopia 236 

range  of  accommodation  in  239 

Myosin,  preparation  of 161 

Narcotics,  influence  on    ciliary 

motion 16 

Near  point 218 

Needle,   saddler's  for  haematol- 

ogy 259 

Nitric  acid  test 163 

Nitrogen,  generation  of. ...  147-148 

respiration    of 147 

Nonpolarizable  electrodes 52 

Normal  saline  solution 307 


INDEX. 


357 


PAGE 

Numeration  of  Lenses 232 

Ohms,  unit  of  resistance 31 

Olein 183 

Operating  case 308 

Ophthalmoscope 247 

Ophthalmoscopy 247 

Optics,  physiological 198 

Osmosis 189-191 

Palmitin 183 

Pancreatic     ferments,    glycerin 

extract  of 185 

Pancreatic  juice,  action  of 186 

artificial 185 

Pepsin,  glycerine  extract  of.  .  .  .    171 

possible  dilution  of 175 

Peptone,  to  separate  from  other 

proteids 1(35 

diffusibility  of 107 

Perimeter,    instrument 220 

circles 228 

chart 230 

Perimetry 226 

Pfliiger's  law  of  contraction.  ...      70 

Pharmacology 285 

Phosphoric  acid  in  gastric    di- 
gestion    173 

Photometer 2:J7 

Phrenic  nerve,  dissection  of...      134 

Phrenogram 132-134 

Phenograph 132 

Physiological  operating  case. .  .   308 

Piezometer   96 

Pilocarpin 293 

Pith,  to  pith  a  frog 10 

Plane,   inclined,  for  computing 

ciliary  work 24 

Plates,  positive  and  negative.  .  .      28 
Plasma  and  corpuscles,  relative 

volume 270 

Pneomanometer 125 


PAGE 

Pneomanometer 317 

Pneumantogram 136 

Pohl's  commutator 28 

Polarizing  current 76 

Poles,  positive  and  negative-.  .  .     2* 
Preparation,  gastrocnemius. ..  .      56 

sartorius 01 

Pressure,  arterial 101 

endosmotic 1 00 

formulae 104-105 

intermittent 9S 

intra-abdominal 1 14-116 

intra-pulmonary 137 

laws  of  blood  pressure 102 

of  liquid  in  tubes 96 

respiratory - 137 

venous 104 

Proteids,   diffusibility  of 106 

coagulation  of 162 

properties  of 161 

tests  for 163-164 

Proteoses,  diffusibility  of 167 

Proteolytic,   ferment 167 

Pulmonary  vagus   137 

Pulse 106 

impulse  wave 99 

Punctum  proximum ....    218 

remotum 218 

Pupillary  distance   244 

Purkinje-Sansom's  images 223 

Rabbit  board  (Fig.  19) 110 

Rabbit's  lungs,  elasticity  of .  . . .    138 

Radial  artery,  location  of 106 

Radius  of  curvature 201 

Range  of  accommodation 238 

Reaction    changes    in    fatigued 

muscles 74 

Red  blood  corpuscles,  varieties 

of 280 

Red  corpuscles,  counting 202 


358 


INDEX. 


Red  and  white  cells,  differential 

counting  of 280 

Reduced  eye 211  212 

Reducing  sugars,  tests  for 155 

Rennin 181 

Reservoir 93 

Resistance,  central  and  distal.  .  97 

how  measured 31 

Resistance,    relations  of  to  dis- 
charge   95 

Respiration 113 

in  closed  space 114 

in  C02  gas 145 

N-gas 148 

H-gas 14.S 

under  abnormal  conditions  141 

in  abnormal  media 147 

Respiratory  movements 113 

in  man 118 

pressure 135 

quotient 143 

Rheocord,   DuBois-Reymond's.  40 

simple  (Fig.  7) 43 

Rheonom,   Fleischl's 48 

Rheostat 40 

Saccharose,  properties  of.  .  155-150 

Saline  solution  (0.6#) 307 

Salivary  digestion 157-101 

Saponification 182 

Sartorius  preparation 01 

Scheiner's  experiment 222 

Series,  arrangement  of  cells  in  .  35 
Siphon      bottle      for    solut'ons 

(Fig.  53) 307 

apparatus  for  forcing  gas. .  20 

Skiascopic  eye 247 

Skiascopy 252 

Sodic  chloride  (0.6*) 307 

Snellen's  test  type 233 

Sphygmograms 106 


PAGE 

Sphygmographs 106 

Spirometer 124 

Spreading  blood,  haematoh  gy .  .  278 

Staining  blood 278 

Standard  gastric  juice 175 

Starch,  digestion  of 158 

properties  of 153 

Stearin 183 

Stethograph 118  119,  313 

Stethogoniometer 118,  12.',  316 

Stethoscope 91 

Stimulants,  influence  of  on  cil- 
iary   motion 16 

Stimulation,  chemical 60 

direct 26 

indirect 26 

of  vagus 112 

mechanical 59 

thermal 60 

variations  of 62  63 

Strychnin 295 

Syntonin,  preparation  of 161 

Tandem,  arrangement  of  cells.  36 

Tambours,  receiving 312 

recording    312 

Tape,  meter 124 

Test  types,  Snellen's 233 

Thermal  stimulation 60 

Thoracometer 118,  120,  314 

Thorax,  contour  of 123 

Toisson's    solution 268 

Torricelli.   law  of 94 

Tracings,   fixing  fluid  for 311 

Tromer's  test 157 

Tubes  elastic,  flow  of  liquids 

through 97 

flow  of  liquid  through 93 

inelastic,  flow  of  water  in.  .  98 

Units  electrical 31 

Vagus  nerve,  action  of 109 


IXDEX. 


359 


PAGE 

Vagus  nerve,  pulmonary 137 

stimulation  of 112 

Value,   median 128-129 

Velocity  of  flow  of  liquids 74 

Venous  pressure 104 

Veratrin 298 

Vision 193 

acuteness  of 232 

Visual  angle 233 

Volts,  unit  of  electro-motive  force    31 


PAGE 

Water  element 65 

to  measure  index  of  refrac- 
tion of  water 19!) 

Wave,  pulse  or  impulse 99 

Weight 125 

White  corpuscles,  counting.  .  265 

Work  done  by  cilia 24 

done  by  a  muscle 73 

Xanthroproteic  test 1G4 

Yellow  spot 2^5 


QP4A 


H14 
1900 


Hall 


A  laboratory  guide  in  physiology. 


JUL 


